I have to take that van ride because I'm on company duty. Why should I use my own personal money for a tip for a van ride that I have no choice to take in service of the company. If they reimbursed me for tipping sure, fine I will, but they don't, I have to pay out of my own pocket for something that's in service of the company, so I don't. That's my personal choice, I don't tell others they should agree with me, and they don't tell me I should tip. Simple as that.