I think it was a generic example rather than meant to be specifically accurate. Replace McDonalds with the name of any other restaurant. Why is the server entitled to 15% but the cook or dishwasher not?
In the U.S., from what I've heard from friends who have been food service workers, the tips are collected by the server, but split up nightly among the whole front/back set of workers.
Every place tends to do this differently, in practice it is never an even split (greatly favoring the servers). And at least in the state I worked was completely voluntary as the tips were yours.
