[smoofles]

If they create their own SoC with their own IP having their own system will make it easier to move forward, as they won’t need to share development concerns with a larger group (e.g. they want feature X to go into one direction, and Android takes it in a different one, meaning they would end up with a fork).

This is not a huge issue with smaller/trivial features, but can get really cumbersome with bigger ones, and even more so if the forks start diverging more. As for control, see Apple & getting a modern GPU API that works on mobile and desktop and can be iterated quickly.

For a large number of industries Android makes more sense because they depend on certain development processes (security, hardware support, regulated environment certification, etc), but for multimedia consumption a lot of those are not needed.

Last, but not least, vanity can be a big part of such decisions, too. Engineers love to build stuff, even if it means reinventing the wheel for the Nth time.