The financial benefit seems pretty clear, conditional on self-driving tech working. The capital cost of the hardware would be amortized. Let’s say a driver costs $10/hour. If the self-driving car is active for 16 hours a day it saves you $58k a year in driver wages. Then over more years that number multiplies. It seems totally realistic for self driving tech to cost five figures per vehicle. With mass production the cost of hardware would go down like it always does. I also think it makes a lot of less driver-time-inefficient routes more viable, like driving someone from the city deep into the suburbs with little chance of a return fare. This grows the addressable market.
There are also ethical, legal, and P.R. disadvantages to exploiting human drivers that seem to be getting more significant over time. Personally I’m not super optimistic about the near-term technical viability of self driving cars but it does seem to make Uber’s prospects look better to investors given some possible paths the future might take.