Well, this is obvious for Valve. They created the first successful online store and they want it everywhere, but Apple and Google do not. You are competing aga

Well, this is obvious for Valve. They created the first successful online store and they want it everywhere, but Apple and Google do not. You are competing against Apple and Google Play online Stores. If they support Steam they would be making the platform a commodity(as Steam does not care about the platform), this is something Apple can't let happen, or just replace Google Play as the gatekeeper for Android(as steam already knows how to sell commercial titles). Steam's response to online stores have been to create the Steam machine, that probably will extend over mobile devices in the future(using wifi playing first, creating devices on their own later). Remember that real Linux needs to get to tablet-phone space, with efforts like Ubuntu's Unity it will soon. Valve will be the first to benefit from it(as steam machine is very similar to ubuntu).