I personally think tipping van drivers is out of hand. Answer these questions...
1) Do flight crews get tips for leaving and arriving on time? No..it’s our job.
2) Do ramp crews get tipped for the hundreds of bags they load and unload daily? No..it’s their job.
3) Is a hotel van to/from the airport an “extra”? No..it’s the driver’s job.

Lets say the average crew remember is out 14 nights/month. If you trip $1 each way that’s 28/month. That’s $336/year on something you probably don’t get reimbursed for. If the van driver is willing to take us somewhere then absolutely I will tip them because that’s beyond the scope of our regular airport transportation requirements. I also prefer to load and unload my own bags unless the driver has a method for stacking them in the van.