> want it to happen while I'm at the store, am I setting that person's hours?

> If I specifically want them to use an electric mower for noise reasons

The fundamental difference is you, as a customer, can want these things, but the person doing the mower is self-employed and they can negotiate and figure out whether or not they can come to a mutual agreement with you. They could also just simply not come to an agreement with you and the worst that would happen is they don't get your money, and move on with their work and life.

It's different than if there was Uber Mowing Co. that managed them and forced them to forgo their lunch and mow your lawn while you were at the store or be fired.