FYI you can pay on your card in pretty much 100% of london black cabs now.
I cant remember where it is but one european city made it so only uber-lux is an option, posh (and more expensive) cars only basically.
I was going to try Uber in Vegas, but I wasn't sure if they had any that were scooter friendly.
I didn't investigage any further, as I've been using the same cabbie for years now, and he's a good egg.