Drivers can absolutely sub-contract. most choose not to in the US but it's the core of how the Uber Black business functions (a limosine company with a number of employee drivers) and is still how it meets demand in developing markets or in developing economies.

https://help.uber.com/partners/article/i-want-to-become-a-fl...

Uber regulates what cars are acceptable the same way an Ebay seller has to maintain some standards in their store. Similarly Ebay also verifies that you can even be a seller on their platform, just like Uber does with background checks, DMV checks, etc.

To your last point on subcontracting...I'm not even sure thats part of being a contractor or employee so its neither here nor there.

> Your Uber driver can't subcontract the drive to another driver.

Even if their ToS does not allow it , it's not the law