"As an appetizer: How about this google.... for hardware to be certified for use with the google apps, all of the drivers must be open source."
That's essentially a business decision. Google has little interest in hardware and software being open to competitors. Every device that gets rooted and runs non-Google software means less revenue to Google. In the past, they simply may not have cared, but they will more and more.
Also Google is a platform provider here, and their actual customers want DRM and they want it to be impossible to copy their crappy Apps.
There's a third point and that is that SoC manufacturers like vendor lock-ins. They want to make it as hard was possible to change hardware. This is why SoC hardware typically is as obscure as possible.