The biggest reason I stopped waiting tables is because many diners lorded tips, being overly-choosy about how much to leave. If it took me longer than 30 seconds to refill a drink, that meant less money for me, even if I was in the back brewing iced tea as fast as humanly possible.
This, among other things, is addressed in this week's column, The Art of Tipping.
And don't forget to tip your servers on the way out.