In the US, it takes fairly extreme circumstances to not tip (by most people's standards at least; some people just never tip, but they're a tiny group), like if the service was extremely bad or the waiter was insulting or hostile.
Employers are legally required to chip in if the employee doesn't make minimum wage for a pay period, so it's not completely insane, but it's still a rather weird system.
[1] http://www.payscale.com/research/US/Job=Waiter%2FWaitress/Ho...