At the end of the day, VP8/VP9 is interesting as a possible bandwidth optimization or share certain patent/free software positions. It's just hard to believe that this would decide even a single phone purchase, much less enough to significantly affect Android development priorities.
As far as I understand, the initial motivation is to avoid being locked out. Suppose that iOS held 80% of the market, they could change the default engine, replace Google Maps with Apple Maps (like they did), etc. Given that smartphones and tablets are now commonly used to access the web, Google could have lost a serious chunk of traffic.
In other words, Google does not have to monetize Android directly, it exists to keep people in Google's ecosystem.
Sure there are royalty costs for using H.265. But one could argue that (a) Android already costs money due to Microsoft licensing and (b) there are likely patent issues with VP9 just like there was with VP8.
