Well, in America, you do.
By virtue of waitstaff being exempted from minimum wage laws, you, as a customer are assuming some payment for their services.
Now you know what all that cussing was about when you left a US restaurant without tipping. The poor sap had to cough up income tax on 8% of your bill, also. It's almost like you stole his services.
I broke some contract? Then he can see me in small claims.
Look, it's not like I don't tip, I do. But I tip for service and good work, not because some snarky waiter demands it. In Canada, you see, waiters already are at minimum wage - often above - so it's much less of an issue. That may be why your experience with Canadians was as bad tippers. They don't see how little American wait staff are paid. I do see it, and I tip well in the USA especially. But not if the server are obnoxious jerks as they too often are.