I think this can be explained by the fact that Microsoft has a long history of trying to kill OSS software and alternatives to it's virtual monopoly in the desktop OS market, killing innovation across many technology sectors in the process. Being cross-platform was the opposite of their goals. They specifically created their own version of open technologies and promoted them as the best/only way of doing things on windows - see directx/opengl, and mictrosoft intentionally degrading opengl performance on windows in order to hurt the OSS community.

http://blog.wolfire.com/2010/01/Why-you-should-use-OpenGL-an...