If they aren't for PC gamers they don't stir up things enough to convert console players towards them.
I don't see a point unless they heavily subsidize this or they release exclusives in turn pissing of their other PC players. Valve is in a tough tough situation.
I don't think that is going to be even possible in the next 10 years. The emulator is improving a lot but it is still in very early phase in development. Look at the PS2 emulator PCSX 2. 13 years of development and still can't play certain games like Ratchet and Clank.
Um...Linux existed before Steam and will exist after. Recent development tools like the Steam Source 2 engine or Unreal Engine 4 are free as well on both Windows and Linux.
If you look at it from a gamers perspective, what benefit does SteamOS bring besides being a open source alternative??
Yes we get an alternative to Microsoft, yes we can modify it but there is no advancement here. It's just an alternative with it's own nuances.