Google gets 97% of its income from selling ads and analytics, everything else they do or produce exists only to serve this goal and to strengthen their monopoly and entrench their position even further. A browser to dictate internet standards so they can push towards more surveillance, a mobile operating system so they can control most of the world's mobile devices with an iron fist, email service and cloud storage platform so they can get better profiling data and so on.

Any code that is shared for free under the guise of "open sourcing" is most of the time either a byproduct of their internal research that will not lose any value by sharing it (or will actually make non-employees extend it and work on it for free for Google's benefit), or something so specific to the company that nobody stands to gain anything from adopting it.

Google is first and foremost an advertising and user profiling company, it is useful to think about them from this perspective as it explains most of their actions with perfect clarity.