It might make sense from an organizational point of view, but not from a business point of view. I'm pretty sure that the main reason Android exists is to ensur

It might make sense from an organizational point of view, but not from a business point of view. I'm pretty sure that the main reason Android exists is to ensure the dominance of Google Search, and the ads that it serves, along with all of the other Google services and their ads. Or more precisely, to make it impossible for Google services to ever be cut out of the majority of the mobile market based on the whim of another company. Even the theoretical possibility of that happening would make Google highly subservient to whatever company or companies had the power to do that. Same with Youtube, Maps, etc. They exist to preserve the dominance of and prevent other companies from avoiding Google's key moneymaker, which is ads on searches. Thus allowing them any real independence would destroy their reason for existence.