you say that now but steamos has a feature to use a windows pc to host the video games on via the steam client and then steamos can play the games over the local network or the internet to the steamos box.
which means steamos players can play windows games in the steam cloud using their windows pcs to store the games on. which also means that all 2500+ steam windows games can be played on steamos this way. how many games does that windows 8 store have again?
linux may lack games, true, but using dosbox they can play old dos games and using qemu they can play some classic windows games with an old windows image like windows 95 or 98; however, with wine they can play quite a few windows games like civilization v, etc.
if you saw the steam controller you would know it makes all other controllers look like shite and then you realise that when half life 3 comes out only for linux that valve has the lock-in.