I find this to be a bit crazy!!!
First I don't think a lot of the games which are on steams are Linux compatible which means they have to made compatible. Second Linux has a big problem with 3rd party drivers or I had that huge problem. For example Nvidia and ATI drivers there are numerous hoops people have to jump through to get the driver working.
My experience is filled with nightmares of stopping X server installing drivers - without removing the old ones and when finished not being able to start the x server nor the entire graphical interface.
Usually Steam needs to have the best and newest drivers installed so I wonder what will happen when people use the proprietary driver to play games in Linux.
I personally do not think this is going to work until the graphical issues and drivers get ironed out and become easier to install. But who knows may be this is the push companies need to start developing more useful deployment of packages (cough cough Nvidia).