Frequently, it doesn’t. Or more frequently, not all of it. It’s acruelly illegal (a form of wage theft.) but because there’s a sense that the person working the shit job needs that shit job… complaining about it doesn’t help.
In any case… I’m of the opinion that I shouldn’t have to tip. If that pisses of service workers, they can (and should,) go find another job. That said I do tip for typical things- I just do t think I should have to. And if the service is terrible….
In any case, there are waitstaff that make relatively large paychecks from tipping as well. (Particularly in bars.)