They probably don't feel their drivers are valuable assets worth retaining, much like how tech companies treat their telesales staff.

You want to quit? Go nuts, we have 50 people who will work for less ASAP, and we think we can onboard them easily.

We're also developing technology that will let us have robo drivers (or robo sales staff). So we won't really miss you, even if you compete with us.

I believe that Ubers ultimate goal is to become a logistics company. They want to move people around. They also want to be the last mile on delivering that express Amazon package to your door, or getting your food order to your house (they're already experimenting with that), and just generally being the company responsible for transporting everything around a city.

From the perspective of managing their drivers, they're not to worried about other folks taking "their" drivers as ultimately they're going to have FAR more work for drivers to do than companies merely in the cab business. As a driver you're going to rely on Uber because the quantity of the work will be so much higher on their network.

That's the long game for them and I suspect that's how they see things right now.

* note: I'm 100% speculating here, I have no real special insight into what they're up to.