I think part of it is that none of the OEMs really want to be just a computing platform. Margins are razor-thin due to competitive pressure from both the market

I think part of it is that none of the OEMs really want to be just a computing platform. Margins are razor-thin due to competitive pressure from both the markets and from suppliers. They see Apple and Google and Microsoft dominating the field with their tightly-integrated ecosystems, commanding what is essentially a royalty on all "app" economic activity (to say nothing of hardware sales and everything else). And they want some. Bad. Besides, public opinion on computing as a platform seems all but dead. This is a computers-as-appliance age, where everyone is punch-drunk on services and single-use apps. Power users seem to be disappearing; nobody wants to learn how to do anything and so much of what sells are just variations on a it-wipes-my-own-ass theme. Platforms don't work in that world; too few want to bother with them. Nobody wants to simply build computers anymore, it seems. Too boring. (edit: On the margins thing-- the big three enjoy greater margins because they offer greater services, insulating them from said pressure)