When I was growing up, there were elevator operators in all the high-rise office buildings in Downtown Pittsburgh. When you drove into a "gas" station, someone came out and cleaned your windshield, checked your oil and tire pressure, and collected the money, all without charge and certainly with no expectation of getting a tip. When you went into a retail store, there was a clerk on duty who helped you find and select your purchase.
Crappy jobs all, and all gone now.
When the cost of any commodity goes up (human effort being a commodity), the users of that commodity look for ways to use less of it, or stop using it altogether.
Human nature.
If a $15/hr minimum wage is good, then why be niggardly about it? Why not $25? $50?
You can't buy a house on $15/hr, or put a kid through college.