People who should certainly be tipped are people in the service industry who work for tips (i.e. Waitresses making $2.13/hr from the restaurant since their tips count towards the minimum wage). People making at least minimum wage or better aren't technically "working for tips"...tips are a nice bonus based on the quality of service they provide. Auto-tipping people who don't use tips to meet wage requirements defeats the purpose of a tip for quality service. Do you tip a McDonald's employee who takes your order? If not, why not? Do you tip the person who waits on you in Dillard's when you buy a shirt? If not, why not.

I tip the van driver because it has become industry standard for flight crews. I'm generous when tipping in restaurants as many restaurant employees pool tips. Expecting people to tip everyone they come into contact with, though does get a bit excessive.