if you don't want fast food workers making 20 an hour. Stop going to McDonald's and they will have no one to serve, and no need to hire anyone. The fact that they can pay them 20 an hour and stay open and were paying them what they were, should be all the info you need, but yet here we are.
People shouldn't learn a trade based solely on income either.
If I can get paid 20 an hour to flip burgers 20 an hour to sweep floors shouldn't be a big deal, or the boss needs to sell a vacation home I guess.