I have met friends and associates for coffee and spent an hour at the table. The waitress (always a woman in cheaper diners) seems to be working hard and I'm sure is not paid more than waiters in the high-priced joints. Though our entire bill might be just a few bucks, I usually leave $5 for the waitress who took care of us. Well beyond 15%. In the expensive joints, I have been known to cringe at the final bill and am reluctant to go a whole lot deeper in the hole with a big tip. Nor do I notice the high-end waiters and waitresses working any harder or acting any more gracious than those making $3 per table at Denny's.
I find our system discriminatory and even a bit sexist, given that most wait-women work in less expensive places and nearly all wait-men in expensive ones. I prefer to even out what I tip, regardless of what the restaurant owner charges for the meal. Makes me generous in the one case and a cheapskate in the other.
I worked as a waitress and as a bartender while in college. My tips (when I got them) were paltry, but then my employers weren't running fancy joints either. Most of us who've worked in food service learned enough to know we wanted a different career. It's hard work and like many jobs dealing with the public, can be stressful. Abusive customers abound.
Ushers in movie theaters, clerks in convenience stores, fast food workers -- do any of them receive tips? Should they?
I understand tipping is supposed to be related to service received. But unfortunately it no longer seems to be in restaurants. Give less than 15% and it's a reflection on you, not the waitstaff. I'm willing to tip for good service, but why only in restaurants? And why in such an unequal fashion?
See also: The Truth about Jobs