Even if every driver knew for certain that the income wouldn't cover the longterm cost of wear, there would still be drivers who needed money now enough to trade the future value of their car.
Which I imagine happens a lot. I expect a lot of/most drivers have at least a vague sense that a decent chunk of their earnings are going to get eaten up down the road in new tires, maintenance, etc. But they have rent due next week so...
You miss the obvious driver who is not an Uber driver only but one who is an Uber driver as a side hustle. This person owns a car for their own reasons, they want to drive around and have access to a vehicle. They 'rent' that expense to Uber which comes out of their compensation.
Here is another way to look at it. Someone who rents their apartment on AirBnB for one week a month which generates enough revenue to pay their rent, and they live in the apartment the other weeks of the month. This arbitraging of costs is similar to what Uber drivers do.
If Uber were to shift completely to self driven cars, all of their arbitrage ability would be lost, as the full costs of the cars would then be on their books. Now if the business model of having cars available 24hrs a day and there was no drivers fee allowed them to be profitable, that would be an interesting model. Of course one of the things that is going to happen in self driven cars will be things like drunk people throwing up all over the car, resulting in the car being out of service while someone cleans it. Or being defrauded when someone steals a phone and tells a self driving uber to drive them to the next state so they can sleep in the back seat. Then you are back to a security guard who is watching cameras of cars, but how many do you need of those? What do they get paid, are they 'contractors' or employees?
I'm rooting for them to change the world for the better but I've been unable to guess at a business model that would allow them to be profitable yet.
The cost equation for AirBnB and robo-Uber--when used in the sense of renting out personal property as a side hustle--are different though.
If you're away for the weekend or a business trip, there's very little $$ cost associated with renting out your condo for the weekend (ignoring the risk of a bad renter). It's arguably (almost) free money, again, depending on how you quantify the risk.
The cost of a car, on the other hand, is mostly related to how many miles it's driven, not over how many years it's driven. There are some time-based costs (taxes, insurance mostly, rust in snow states, having older tech) but it's mostly distance.