Uber, because of all the data it's able to collect, operates on a fine tipped point between supply and demand. You see this all the time with Uber coming into a

Uber, because of all the data it's able to collect, operates on a fine tipped point between supply and demand. You see this all the time with Uber coming into a new city with initially high rates to rapidly bootstrap their driver pool and then a slow ratcheting down over time. Widespread tipping wouldn't result in drivers being better compensated, except in the short term. In the long term, it will simply result in Uber lowering its rates to compensate and the drivers making exactly the same amount.