I don't think that's a function of pay. That's because there's an abundance of jobs at that level and retail workers can now have more flexibility in finding the job that fits their schedule and desire. Rather than pay 2 people to stand behind a register to just input things into a register and ask dumb questions, those 2 people can make the food, clean up, gather the food, etc. When I worked retail it was a pain in the butt handling a customer at the register because it took me away from something else I was doing, like stocking shelves or whatever. People aren't out there crying because they can't work at McDonald's anymore. They're working somewhere else, or they retired, or they realized after covid they didn't need the extra money it brought in.
It's really no different than not having gas station attendents pump our gas. Once they realize customers can do it themselves then why pay people to do it?