Umm, I did think that PC games use OpenGL as well, it's not just a Linux thing. Yes, you do need extra stuff for wheels etc, but making it OpenGL means it can be multi platform with less effort.
Yes, DirectX 9c is awesome, till good old MS decide to cripple it in some way. Sure, never update but, why not just go opensource, remove the reliance on good old MS. Yes, not going to happen here, till MS just delete 9c, tell everyone to go with 12 or whatever, stop the old version working with any currently supported OS. They'd never do that ?, lets see.......