Gaming sucks on linux (lack of games) because so much money has been poured into making games run on microsoft's direct3d api. now with steam on linux and mac you will see more and more games running on openGL. also steam doesn't distrust windows
it's all about market share and linux is just one more place to make money. also the GPU drivers(AMD and Nvidia with nvidia generally being better) suck for linux because there are so many different flavors of it. unity, gnome and others and a butt load of different distros.