The reason SteamOS exists is because Valve can't compete against consoles when their SteamBoxs have to include an expensive Windows OS. Also Valve isn't a big fan of Microsoft and their Windows 8. So for you, yes you can go ahead and use Windows and have a better experience. But JoeSixPack is looking to spend no more than $500 for a game machine, and Windows would be the tipping point that would exceed the price beyond that of console prices.
It's a $50 difference for OEM's to include Windows over Linux. I think Steamboxes are the only thing platform wise that could legitimately win some console gamers however they really do need some exclusives and games that really make use of VOIP...despite those that support it, most PC gamers don't talk much. Exclusives really do drive gamers towards specific platforms but price is a big factor as well and this is where a console like the PS4 is always going to win because it's at least $100 cheaper and it's graphics are very comparable...most gamers don't care about TXAA or other small details that break the difference of high end PC's vs consoles and despite the debates, they don't seem to mind 30fps in all reality, they just like to complain publicly.