Plenty of customs don’t make logical sense, and plenty of words have dramatically changed meaning over time. Don’t read too much into the word. A “fine” used to mean a voluntary settlement.

You are right, I wasn't really thinking about how customs evolve organically. Outrage kinda blinded me because that experience was such a culture clash that clouded my understanding. Thanks. I mean, I still feel like using the word "tip" for something that is culturally not optional, even though you can opt out, is unnecessarily confusing and hostile, but that's what respecting foreign culture is all about.