Steam doesn't have a choice if ZeniMax/Bethesda decides to update the game they have to send the update through. If you're going to point fingers then point them in right direction. And it's Bethesda/ZeniMax that decides you need Steam if wasn't Steam it would be some other platform. Steam is just a distributor a store front so you can't actually take "ownership" of the game from them but either way that would be breaking the TOS and depending on where you live it can also fall under piracy. Not to mention considering what would need to be done in order to do that you would for all intent and purposes make your game un-moddable.