In rough order of importance to drivers:

1) Not causing damage to their vehicles.

2) Giving good enough directions on pickup such that they waste a minimum of (unpaid) time getting to you, and exiting the car in an expeditious manner. An Uber driver's KPI is "number of minutes per day with the car in motion with a passenger in it." (This is the biggest reason why many of them keep multiple phones with multiple apps open -- minimizing time between trips maximizes the number of trips they take per day and, thus, revenue.)

3) Not contravening the usual covenants of civil society.

Much of that value is automated in the form of our credit card details in our Uber app. But we do provide value in a few other forms: not being obnoxious, not trashing/puking in their car, not harassing them physically or verbally.

All these things happen to taxi and Uber drivers regularly, so there IS a need to keep the demand-side riders in check. It's analogous to eBay or AirBnB's two-sided rating systems.

Also, it's not fair to state as fact that our consumer buyer ratings will be "saved, sold and shared eventually." If Uber were a free consumer app with an unclear revenue source, that'd almost certainly be the case. But Uber isn't in the business of needing to sell that data. On the contrary, any marketplace data they hold is competitive advantage over other driver/rider services. They have at least some incentive to keep that proprietary.

Both people in a transaction value the thing they have less than the thing the other person is offering, otherwise there's no reason to bother making the transaction.

At least, in theory.

also at the minimum they should make clear the passenger (you) is going to be rated IMO. Maybe that'd solve the issue of passengers not being courteous or whatever.

You provide them with the "I didn't vomit in your car" service.

I don't see how this it the case, assuming that drivers don't know what passengers rated them before rating the passenger.