Apparently, you've never been to a state where it's legal. Go to CO sometime.............because if you do, you will see how regulated it is, as well as the fact that there are zero dealers set up outside of the legal dispensaries. But, if you're looking for someone to deliver some cannabis to you that isn't taxed like the dispensaries, and is grown and distributed outside of the law, you'd have to go to Craigs List or some other such website. They don't hang outside of the dispensaries, they wait for people to call and deliver to them. And, those local dealers aren't answering to the cartels, they are in business for themselves.
Not only that, but in states where it's been legalized, they have MUCH more tax revenue for the state, as well as less of a problem with the crime associated with buying on the street. Most people prefer to go to a legal dispensary as they know what they are getting (strain, type of cannabis), and don't have to fear any interaction with the police.