I think it's pretty standard to tip van drivers a buck per ride to and from the airport. The exception is if they're very rude, reckless, or don't help with bags. As said that's pretty rare, but it happens. give them $2 per ride if they take you somewhere other than the airport, especially if it's outside the hotel's shuttle zone. This ensures personal trips in the future!

FWIW, if you think about van driver tips, say a busy brand name hotel that houses a lot of crews in a large city. If they do 4 airport runs per hour, with lets say 6 people each way, that's $48/hr in addition to local minimum wage. So they aren't exactly suffering. If you or your fellow crew member is too cheap or poor to shell out a buck, whatever, but don't feel like you're starving their kids.

As for hotel maids, it's standard to tip $5 or less per night FOR STAYS LONGER THAN ONE NIGHT. I don't tip for one night stays, and neither do most business travelers in other industries. But if you want to, no one is stopping you. Guilting people who don't isn't necessary. You do you and I'll do me.