What gave them that right? Their expectation? My generosity? A contract? Social norms? God? The government? Speaking of the government, if the waiter works at a government cafeteria, does that make it bribing a government employee? Personally, I would much rather pay a little more for the food, make sure waiters had a steadier stream of income, and reduce tipping to being a signal of gratitude for outstanding service. It would not be at all difficult to arrange contracts to say "so many dollars per hour, so much per table, plus tips."