I tried to think of a reason not to support OpenGL. Their Directx seams to be completely free and a lot of Indies are workin with OGL. So I see no reason not too support it. Since they use AMD, whose drivers have very good OpenGL, it wouldn't be that much work either. Im not trying to make them support it, I'm just trying to find out their reasons. So does anyone have a clue?
It's very simple: corporate policy. DirectX is Microsoft's graphics API; OpenGL isn't, and the Xbox is a closed Microsoft ecosystem. Therefore, the Xbox supports DirectX but not OpenGL.