I'm usually up to tipping them $1.00, but only if they're on time. If we have to wait more than a few minutes, I don't tip at all.
Van drivers should be paid better. Why have hotel guests subsidize these employees' pay?
Nobody tips regional pilots, who are paid even less than a shuttle driver.- and we can cut corners, speed up, and taxi like a bat out of hell to help make these passengers' connections.
A captain I know leaves a tip jar hanging on the cockpit door as passengers exit.