Steam OS needs EA Sports if they want to challenge MS / Sony in the living room.
They're not challenging anyone in the living room, even Wii U which well sell the least this gen will far outsell the Steambox(s). Steam/Valve has no brand recognition outside of their hardcore following on the internet.
Go and ask some grandma on the street what PlayStation, Xbox or Nintendo is, they can tell you, but they'd never have even heard of Steam or Valve before. You can't compete in the console space without a brand name, bloody hell even Nintendo has trouble competing with PS and Xbox these days, Steambox has no chance.
And another thing you need to compete in the console market - marketing, and a big ass budget. I don't see Valve advertising Steambox on TV or in football stadiums, or making partnerships with Tesco or Taco Bell, for example.
Steambox is a niche product for a niche market, PC gamers will stick with PC's, console gamers will stick with the big three. I think it's naive to think Steambox is actually going to compete, it's more akin to Ouya than PS4.
Yes, I know, right now, but you have to start somewhere.