Depends on what it is, and what kind of resources you have. In this case, you're talking about a massively difficult task (between the technical and regulatory aspects and the safety-critical nature), and at least two mammoth (i.e. well-funded internally) companies are already working on it. What exactly is a company with zero expertise in the field (a mobile app? Please), with absolute reliance on VC funding, likely to bring to the table? A lot of risk, that's what.
Yes, I think driverless vehicles are probably an inevitability, but I wouldn't look to Uber to come out on top here, any more than I expect Tinder to come out on top in asteroid mining.
Uber isn't even profitable with their core business of being a not-quite-taxi company. They quite obviously don't have the money to build their own self-driving cars, too.
In your opinion, is work not worth doing if those mammoth companies are pursuing it?
Also, you say it is a risky endeavor. Would you argue that the driverless vehicle is not an inevitability? I would certainly argue that betting on Uber to come out on top is risky, but that doesn't mean there isn't money to be made.