EDIT: To a reply saying I don’t understand how fast food restaurants operate, I certainly do, I’ve worked fast food in my life. While they certainly try to be flexible, you can’t just decide to show up approximately “whenever you feel like it.” The closest approximation to that is to only have 4 hours a week regularly scheduled (otherwise they can’t call you an employee), and then you call in whenever you feel like working to see if they need help (often they will say “yes” but sometimes they will say “no”). However, this arrangement only works once you have enough experience that you can come in and basically work any position in the restaurant, and it’s not something that can be scaled to every worker at the restaurant.
You actually can take several months off from McDonalds if you want and come back. Many employees do, especially the ones that work at college-town McDs...
Moreover, you can switch shifts at will, so long as you find another employee to exchange shifts with.
Pretty much the difference between fast food and Uber is that fast food is a minimum 8 hour shift and Uber can be as short as a 1 minute ride.
And what happens if you don't log in to Uber or Lyft every day? You'll fall off their internal automated lists for ride selection priority and get stuck with all the undesirable rides nobody else wanted to drive.