As someone who's both received and given tips, I love them. Why? Because they're a dead-simple way to convert money to happiness. When I received a big tip, it always brightened my shift a bit. And now, every time I go out to eat, I know that I can do the same for someone else.
Do you stand in the street and give people money? You can buy other's temporary happiness there too.
If someone is just friendly and helpful way beyond the call of duty, I'll probably drop a 25% tip in their lap just because if somebody makes my day, I want to make their day in return.
And then there was when my favorite bartender left his job at my favorite bar... I think I tipped almost 50% on his last night as a parting gift.