Tips are a way to show appreciation. Supposedly. I see it more as a duty/obligation/politeness thing that is steeped in culture, and has gone so far as to make some people feel guilty when tipping less than the usual amount. I guess it’s also a form of reward or encouragement, like operant conditioning (e.g. like training dogs by rewarding good behaviour). “Good boy/girl!” Maybe we should get rid of the whole tipping system and just add a service charge to all the bills, and give bonuses to waiters who get commended a lot. But I know some jobs live off tips, so for now, I’ll try to be as generous as possible.