Well, be using OpenGL they get all this plus easy portability to OSX, Linux, Android, iOS and any consoles providing somethig close to an OpenGL implementation (most of them). But Microsoft offers some tasty cookies (features) to lead people to DirectX and many gamedevs can't be bothered to implement the same features themselves in OpenGL.
If gamdevs formed an alliance, implemented features useful to gamdev on top of OpenGL and released them as a free library everybody (except Microsoft, bye-bye lock-in) would benefit.