Well, to tip the conversation back to tipping, here's my policy: if the van is there ready and waiting by the time I get there? Tip is definitely coming. If the van driver drives fast and efficiently without making me feel like I'm about to die? Tip.

If the van driver is angry to be there or yells at myself or my crew (it's rare, but happened), no tip for you! Same if the van driver makes me more nervous than flying with a FO fresh off IOE trying to do the dreaded night visual into SJC, then it's no tip as well. Otherwise, I try to be generous and tip the van drivers. I also try to be generous with my crew, too, though. Especially the FAs.

Tl:dr. If the van driver is not a jerk, tip. Otherwise...