[oliwarner]

And with a structure like Uber, you could easily let drivers set their own "tip" by setting a riser to pay for in-ride amenities (WiFi, water, etc, etc).

Because that's the common argument against tips: nobody will go out of their way to provide above average service. If you think you're a better waiter, driver, experience, allow your prices to show as higher and you get the difference.

The risk you run is nobody wanting your extras, but I think that's far better than providing them and panhandling for a tip.