They keep breaking laws and having to pay out the ass in fines. Their model won't be profitable until they buy off enough lawmakers to get the regulations changed.
The next round of Uber stories we'll be reading will involve their being named as co-defendants in wrongful death lawsuits involving unsafe vehicles. In my state, cabs and limos have to go through a state safety lane twice a year. Cab/chauffeur drivers have to have special training and licenses. And cab/limo companies carry PLENTY of liability insurance, and are pretty picky about who drives for them. Uber can try to hand-wave all of that, but sooner or later, huge jury payouts are going to run them into bankruptcy.
Well, let's think about IoT RealMedia or IoT ActiveX as alternatives. Then again, let's not.
Pellets don't gain velocity when falling to earth...Have you ever even owned a firearm?
EVERYTHING gains velocity (9.8 m/s^2) when falling to earth...Have you ever even heard of Newton?
Klein bottle for rent -- inquire within.