I agree with what you say here, but it isn't always the case that MW'gers are simply interchangeable based upon the minimum wage payscale. Some people don't even make it in some job skills or jobs in which they are hired for, and this regardless of what pay they start out with, but another new employee might make it even though they started at MW level.. No one is as interchangeable as companies or corporations wish that they were. There is value in each individual, it's just a matter of them finally fitting in where they belong in life.
That would be the individual employee's "retention" value as I said. However, one does not automatically earn "retention" value with the company when hired to do a job, it's more of an earned thing. With the presumption that an employee has low skills, their retention value to the company is based on a long list of attributes, but these are the major points:
Is the employee "reliable" - do they show up for work on time? do they call in if they're going to be late? does this happen a lot? are they sick/not making it to work a lot? do they do /all/ the work they are asked to do? without complaining? glad to do it?
Is the employee "personable" - do they get along with their co-workers? do they respect their co-workers? do they get along with their managers? do they respect their managers? In the case of a position that must interact with customers; do they smile when helping customers? do they act and speak in a way that reflects the company well to it's customers? do they insure the customer is satisfied with the service the employee provided them? do the customers in general seem to like the employee?
Is the employee "available" - are they flexible with their work time or are they only willing/able to work certain shifts? are they constantly changing their shifts with other employees because they have "other" things they have to do? (The latter here is kind of preliminary logistics stuff, it matters to employees when considering longer term or upward mobilization - if an employee can only seem to work a day shift, then the employer might not consider them for a night assistant shift manager opening kind of thing.)
Is the employee "dedicated" - do they do their work reliably? on time? do they notice little things that are failing to be done by other employees? do they ignore it or do they attempt to resolve the loose strings? tell their manager? fix it themselves? (The latter matters to the employer because it says something about if said employee would be able to work without supervision. It also speaks toward the employee's ability to handle more responsibilities, as well as their attitude toward making sure the business is running smoothly.)
The first two aspects are quite frankly the bare minimum's and they are generally /expected/ by employers. Failing to show you can handle those two minimums puts you on the "let these employees go first" list (or as I call it the "meh" list,) in some jobs not being able to achieve one or both of them acceptably will get you fired regardless. For example, I will not tolerate an employee who causes drama with other employee's, its not fair to my employees and it's not fair to my customers. If a new hire is causing, or having trouble, with their co-workers, I'll give them a warning chat to try to resolve the problem, maybe even chat with their manager about it to try to figure out what the problem is (note no one "in authority" can really talk to other employees about a specific employee's actions; it puts a bad taste in all the employees mouths if they think your are going behind their backs and talking about them with their "peers," the best we can really do in management is ask the employees open ended questions like "Is anything bothering you?" "are you enjoying working here" etc., so we typically can only ask their manager if they know what is happening between the conflicting co-workers - its a small bit of the managers job) Anyway, if whatever the conflict is can't be resolved easily, or if it can't be figured out, I usually just get rid of the new guy because it's not worth my time and - yeah, here it is, this "new guy" can be replaced very easily. (Yes, I admit that it's not always the new guys fault, I have on occasion found it was a previous hire who was mucking up the works - I fired them when I figured it out. I've also called up the previously fired "new guy" and offered them back the position if they had generally passed, or seemed like they would pass, the rest of the first two minimums.)
Now the last two aspects are kind of where "retention" value begins to really deviate from one generic low skill worker to another. Even so, these are just minor tic-mark's in the employee's favor as they are not exactly impressive or rare talents. They are not "worthless," but by the same token they are not really be-all or end-all factors when we're talking about a low skill worker. Unless I have a "pressing" need to move employee's around (like say I've got another more skilled person who's quitting and I need to fill their position by moving someone else up,) these things have a pretty low "retention" value. The chances that I'll find someone else with the basic first two points, and a tic's or two from the second two points is pretty high, so other than the hassle of having to a) temporary cover w/e position they are handling again, and b) drop a "now hiring" sign/post and go through the interviewing process again, it's kind of a non-value. There's some subjective flex to it, if their manager likes the kid, they'll have a higher retention value, if their manager doesn't like them then they'll have less, etc. (Another part of management's job; assessing employee's potentials.) Or, like if we've put some money into training classes of some kind (note that typically only "classes" require any money, most often the manger is expected to train, or they have to be around to cover things while a "peer" employee trains the new hire.)
It's honestly not until an employee has worked somewhere for like 6mos (low end) to a year or more that there really starts to be a "measurable" value deviation. This is roughly the stage when we start considering investing in a specific employee because it's a turning point when they start becoming harder to replace with just any other low skill worker off the street; it's when we start planning on keeping this employee. (You'll notice that a lot of companies start paying benefits after 6mos, medical, 401k matching, stock options, etc. are an investment in the employee that actually cost the employer "money" in some form or another - these things are a non-monetary "raise" that marks the first stages of "investment" in the employee.) Anyway, by this time they've earned a little "tenure" with us - we should have an idea that they are a good fit for the company and there is no thought of having to fire them or desire to let them go, they should know their job, as well as have a general idea of whats up with other employee's job duties, they should have "earned" a number of tic's from all four of the aspects above, they should have some "respect" from other employee's - maybe they're helping train new employees, maybe they're the one the other employee's ask for help, maybe they are the one the other employees choose to talk to [about whatever.] (These ones are tic's toward a possible future supervisory/management position.) We should have some "trust" in them, ranging from minor stuff like we're confident they'll do their tasks well even if we're not paying attention (more advanced "reliability"), to bigger stuff like we trust them to handle the money without supervision (count tills, put the opening amounts in other employee's tills, maybe even do the menial tasks necessary for opening or closing the store, or we might trust them with a key to the building so they could do those things without supervision.
Retention value factors in this stage are mostly "trust" (as I just mentioned,) "usefulness," and "potential" - maybe we can put them on drive-through or counter because they've learned both. If they have an "available" tic we can call them up in an emergency to fill a shift if someone else calls in sick, or perhaps we could move them around to different shifts if we needed to. If they have a "dedicated" tic, maybe we don't need to pay another employee as much to supervise them or more commonly, our manager doesn't have to "babysit" them so /they/ aren't working as hard (a happy manager is a loyal manager who cares about our businesses well being.) Maybe we consider them a particularly good employee and don't want to risk losing them to a higher paying job offer, or perhaps we think this employee is a good candidate to move up to a higher position (this is a key point where the employee typically gets what I like to call a "retention" raise - if we have a position we'd like to see them in we might pay to send them to a class to learn w/e specialized skill(s) would be required for said higher position we have open, or that we think might open up.) Again some subjective factors play in, I have given employee's raises because the rumor is they might have to quit for some reason, because I discovered they had been doing someone else's job without being asked, even gave one employee a raise because their dog passed away (a less stressed employee [that I plan to keep] is a more productive employee.)
After this stage, we're not typically talking about a "low skill" employee anymore; with 1 1/2 - 2 years of experience in a particular position an employee can typically start to ply a bit more hiring value out of the little MW gold star I mentioned. This is another stage when employer's might start having a "concern" that the employee they want to keep might leave and they would lose something of "value" to them. If they've been grooming, or have invested money into training, that employee then they'll typically offer another "retention" raise.
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All that said, I do think it should be mentioned that quite a few companies outside of fast food joints, and other jobs with high turn-over rates, practice what I call "paying it forward" - this means that they hire an employee with a promise of "scheduled" raises, and there is an automatic premise that the employee will be staying with the company. This happens typically when the company has to put money into training the employee right off the bat just to do the job, usually upon hire they'll inform the employee that they will get a raise of x amount after 3mos and another after 6mos (sometimes they call this a "trial period.") This is an attempt to protect the initial investment they are going to be making into the employees training. Or they might offer full benefits upon hire to attract candidates for a long term position or career with them. By informing an employee that they have scheduled raises coming they essentially increase the employee's desire to stick it out and the likelihood that the employee isn't going to just randomly quit or be out looking for another job that might pay a little bit more. A lot of the time it's a sort of "secret code" to an employee that this isn't a "temporary" or "first job" type position, the company itself is hoping that you're going to stay with them. These are the jobs you /want/ to get into, the only cavort is that if it's a smaller business then it's likely to be a lot longer between raises but there's other benefits.
An extended note on small businesses -- your mom & pop stores, they do not hire very often and they do not typically have large profits so you don't really get "raises" when you move "up the ladder" with them. The trade off is that you have really high job security and it's typically a far more "enjoyable" job - they will usually bend over backward to accommodate your specific needs and genuinely try to keep you happy; like buying things you want for the place (a really nice chair, an apple if you don't like PCs, or similar "comforts",) or they'll be more than understanding of time off for things that most other places wouldn't (like birthday's, dinner date's, concert's, etc.,) they'll also give you a lot more say in how the business operates from day to day. They try to pay as best they can, however, you are unlikely to get any kind of regular raises with them. Thing is that with mom & pops they are almost always grooming you to be their manager, or if they already have a young manager or their children will take over when they retire, a key player in their business - and often instead of raises they'll give stuff like discounts or free stuff or even a share of the profits or ownership in the business itself. Small businesses like these are places where an employee has to make a decision that they can live with the written pay rate for the long term in exchange for the "quality" of the job. (Personally working for a small businesses vs corporate is by far my favorite, there's not as much money potential but there is a hell of a lot of freedom and genuine enjoyment to be had. - When you love your work, it's no longer a job - you basically get paid to enjoy yourself all day and there's a lot to be said for that heh)
