I don't mean this in a bad way, but are you american? It does seem a very US viewpoint that goodwill etc. don't really exist (or matter? something else?), and that people need concrete incentives to treat others decently.
Sure money's an motivator but perhaps a bigger one is to have a client treat you with decency. Sure money helps but to have a client just make you feel OK instead of crap, that would matter a lot more to most people. A big tip wouldn't negate bad attitude, even if it got staff to pretend to give a damn about you.
Happened to read this yesterday, not tasteful but relevant <https://theoatmeal.com/comics/tipping_tooting>