This is a very US centric viewpoint. Some Americans enjoy tipping culture because it gives them a sense of charitableness, and they get to feel like they were able to be a "boss" and directly control someones pay. Then they tip a lot, especially to pretty waitresses, and she smiles at them and they go home and feel happy.

As far as the van driver, I would tip him in places like Florida and Texas. If it was in a city with a $15 minimum wage, I would not tip.

Once you live overseas, you realize that the tipping viewpoint is exported by Americans globally, but many cultures do not like it because it distorts payscales for many jobs, and creates an environment where the customer can justify their misbehavior by giving a larger tip. Also, I have seen in third world countries people who were teachers or truck drivers leave their job to go work in restaurants and hotels just because of foreigners tipping crazy amounts. My tour guide when I was in Africa told me he used to teach children but he was able to double his income by working as a tour guide, because Americans (he called US out by name) gave him huge tips that were more than one weeks salary.