Not true. I'm not from the States either (Slovenia, to be exact) and I was working as a waiter/barman back in the student days. At the end of each month I earned more from tips than salary.

Why? Because I always went the extra mile to satisfy customers, entertaining them, telling them a joke, compliment, whatever. Telling jokes wasn't part of my job description but I did it anyway. And the only way for customers to let me know they enjoyed me serving them was by giving me tips. And it was an expensive lounge/club so they were charging enough for the beverages/service.

I guess the same goes with taxi drivers. They don't have to chat with customers. They drive them from A to B. But most of them do. To some customers, this means a lot - and they show their gratitude with tips.