I don't think this is all that surprising to be honest. Google is (by and large) a software development and services company, not a car manufacturer. If they make their own autonomous vehicles, that means they then have to handle everything from safety testing to customer support and sales in addition to the self driving car technology itself. By working with existing car manufacturers, they can focus on their part o…
I have the same response to people who claim Tesla will take over ridehsaring once they have a self-driving car (as opposed to just selling to existing ones that have already built a customer base and worked out the domain specific problems).
Uber and Lyft are the WebVan of this decade.