Mr. Pink has a pretty interresting view on tipping and I kind of agree with him. Tipping should be something people add on for good service, not because it's expected. The problem is that companies in America factor in tips to their employee's wages, and decide that they can pay them less. Thus people expect tips to bring them up to the wage they deserve, and since that always doesn't happen, they get frustrated.
I'm not saying that I don't tip, I tip pretty well actually, but the American system of tipping is inherently flawed.
On a side note: I'm assuming you get compensated for gas/mileage in someway?