Valve was distributing its own games on Windows. Battle.net pre-dated Steam for a number of features.
Its not going to work though - some of you are in an utter fantasy land.Look at the thread title - Valve admits "Steam Machines aren't exactly flying off shelves".
So shiny,PRE-BUILT and PRE-CONFIGURED Linux gaming rigs pushed by a gaming company have shown very little traction for the better of over 4 years.
The same happened with Linux based netbooks,etc or ChromeOS based ones. None of these have gained traction in the desktop/laptop market.
So do you honestly think,then all of a sudden GAMERs(which does not equate to enthusiasts) will suddenly install another OS,and then make a dual boot machine??
You mean the same people who would buy an Nvidia FX(over an ATI 9000 series) or a Pentium 4(over an Athlon 64) as Nvidia and Intel are more "trusted" brands.
Go onto the street and ask how many people have anything other than Windows for their gaming PC?? How many even would know how to make a dual boot machine let alone even care??
If prebuilt Linux machines can't gain traction with marketing from Valve and lots of well known gaming brands like Alienware,suddenly people are making mental acrobatics that gamers will now start farting around with PCs(which are most likely pre-built from a major OEM),so they can run a single game.
Edit!!
Plus back in 2013 people were making the same claims about how SteamOS would give MS a good one.
I pretty much nailed it back then when I said it probably wouldn't gain as much traction as people thought,and I was right. Its no point saying Linux is free when its an afterthought for gaming.
If Valve become so desperate to salvage SteamOS they need to lock-in their first major game release in years to it,that tells you volumes of how poorly it has done.
If Valve forces people to install another OS for HL3/TF3 it would generate far more negative publicity from anything other than uber geeks,and if Valve really were clever,they would be releasing the games to iOS and Android(irony) rather than their own OS who most gamers have just ignored.
With well under 3% marketshare on desktop/laptops for Linux,it makes more sense if Valve improved performance even under OS X.
In fact if we look at the Steam stats:
http://store.steampowered.com/hwsurvey/
98% of users surveyed used Windows,1.64% used OS X and 0.33% Linux.
So it appears for gamers things look even worse!