Nobody cares about what runs under the hood (I mean the real market, not the dozen of us nerds), as long as it looks and plays nice. Market already uses linux both in the form of android but also as a server OS. For both of these the financial incentive was there for someone to write the drivers, make the UI user friendly (android users never have to open a terminal), create sales channels.

Desktop and laptop market is weird because no hardware vendor wants to compete with MS. The only one who does (apple), owns both the hardware and software as well as sales channels, so they are not affected by MS’s deals.