Autonomous driving in the sense of door-to-door taxis is not going to happen in a timeframe remotely relevant to companies like Uber. Maybe in a few decades. Uber needs someone not betting on that.
If Uber wants to be a player in autonomous vehicles they have to become profitable enough to survive long enough to realize that goal. Kalanick's plan was always a pipe dream. Driverless cars just aren't going to be ready in time.
Companies can raise funds if people think it'll succeed.
Uber is very different. Their burn was $991m in Q4 2016 and growing.