Opengl

Riddle me this:

If OpenGL is supposed to be just as good if not even better than Direct3D (Not talking about DirectX here), then why don't developers use OpenGL to program their games generating some extra sales on GNU/Linux and Macintosh?

What is it that D3D can do that OGL can't?
If I were a game developer(I'm not), I'd rather write the 3D subsystem in OpenGL than in Direct3D, for portability reasons(*nix, consoles,...) and that it's less bloated than D3D. And this is coming from someone who actually likes Microsoft's APIs (Win32 and friends).