Hmmm Maybe because Android is given away for Free to all phone makers. Now Google/Motorola compete with the same phone makers they give android to for free. Where would Android be without Samsung? What happens if the linux based operating system Samsung is testing and plans to use in its phones becomes favored over Android in Asian markets?
A lot of questions for Google going forward. Free Android phones given away to people with lower income do not bother with mobile ads and find them mostly annoying.