Is it ever okay to stiff a waitress?
If she breaks your implicit contract—for instance, by refusing to honor some reasonable request of yours without any justification—then it seems to me you’re not required to tip her.
Would any major moral philosophers be okay with me stiffing a waitress?
More on tips
Maybe you could push a Utilitarian like Peter Singer in that direction. Singer tells us that we should be giving more money to support Third World countries. One might reason that the money you are contemplating giving as a tip would be used for greater good by UNICEF than by your waitress. Then again, you probably should have given your money to UNICEF instead of paying 60 bucks for the fish at Bartolotta Ristorante di Mare. Applying the Utilitarian calculation only after your bill arrives is pretty self-serving …
Do I have a moral obligation to tip my blackjack dealer or my plumber?
That all depends on expectations. I’ve never played blackjack, but if I did, I suppose I’d first ask about what everyone else does. In this case, a kind of moral relativism is entirely appropriate. There’s an underlying universal moral principle here: You should keep agreements—even agreements that are not legal, and even agreements that are merely implicit. The relativism comes from the implicit agreement you enter into when you sit down at a blackjack table or call for a plumber—it’s relative to the culture you’re in. In this case, “When in Rome” is a valid, universal moral principle.