I tip, but mainly because I like having regular places, and getting treated good at them. For example, I always goto the same place to get my haircut. Since I tip decently, I probably get taken care of quite a bit better than if I didn't tip at all. Same with a couple restaurants we're regulars at.
Does piss me off a bit though. When I was busting my ass 16 hours a day, shoveling rocks & dirt, planting trees, and laying sod, for someone's new house in the sub-burbs, I never got any tips. I think we got lemonade once or two, but that was it. And I'm expected to give someone a tip because they brought me a drink and a plate of food? We took the person's chunk of clay, and turned it into a beautiful lawn with nice trees, shrub beds, etc. Little more difficult than giving someone a plate of food.