No, they're alternative methods for doing the same thing. And a lot of games do use OpenGL, worth noting are Unigine tech demos that run on both renderers and use the latest features - you can't see much difference between the renderers.
Just that generally Windows is by Microsoft, DirectX is by Microsoft, Linux is by the opensource community, OpenGL is by the opensource community, and most games are targeted at Windows, and the developers can't be bothered to implement a few different renderers.