I don't know how accurate this is, but I read somewhere that the idea of tipping came from a restaurant that had a donation box marked "To Insure Promptness" or something, and making a donation to that box would get you your food a little bit quicker. This way, you were paying money for increased service, instead of evaluating the service after the fact. If you ask me, the old way makes more sense, but I'd rather have waiters working with the idea that if they won't be tipped if they do a bad job. I wouldn't want to be served by someone who puts no effort into his job knowing there won't be any reward for his effort.