Microsoft could not care less about OpenGL on Windows. However, it works just fine.
You know why? As soon as you install your video card drivers, your OpenGL implementation is no longer from Microsoft. It comes from AMD, NVidia or Intel, with all needed optimizations for their hardware.
Apple insisted in not allowing this and doing the OpenGL implementation themselves (which was always crappy and outdated).
Had they allowed the GPU vendors the ability to provide their own implementation, this would have been a non issue.