When I waited tables the 'pay' was 2.13 an hour. If we were training someone, we got minimum wage [because your tips were generally lower or you weren't able to handle as many tables]. If your 'wage' plus claimed tips was less than min. wage, the restaurant had to add enough to make it min wage. You had to claim at least 8% of your sales, I think, as tip, so most people did make a little 'tax free'.
In my experience, the more well off people were the cheap bastards, and the teachers or mechanics tipped well. They knew what it was like to have to 'work' for a living.
And while waiting tables maybe isn't brain surgery, it's not necessarily an 'easy' job, especially when your income is so varied. At my current job, I know what i make; if I do a good job, I get a raise, if I do poorly, I don't get a raise, or I get fired. Waiting tables means my income is based purely on the whims of the people i'm serving. If I do well, I *should* make more--but if I bust my butt for the customer, and he's a cheap bastard who 'never tips' or tips 10%, then my income is neither steady nor related to my performance.
I don't know if tipping is the best way to pay these folks, but I do know that's what we're doing now, so I play by the rules and tip accordingly.
Some nights I would leave with 50-100 bucks in cash, plus my big 80 dollar paycheck at the end of two weeks; some nights I'd leave with 20 bucks. One night I left with like 1.50. I had the smoking section, which was freezing, and no one sat there. After two hours I said, Okay, boss, this is a waste, can I leave? That way I at least had my Sunday evening free.