Why your uber driver asks you to rate him 5 stars?

Ever wondered why your uber driver begs you to rate five stars after the trip ends?
Users of the app may rate drivers; in turn, drivers may rate users.
A low rating might diminish the availability and convenience of the service to the user.
If a driver rates a rider at three stars or below, the rider will never be paired with that driver again.
In the same vein, an average uber driver needs to have a rating of about 4.5+ to be in the system, if they can't get that, they get kicked out of the system.
So keep people earning.
I learnt this from an uber driver today.