Apple does not have to port everything to windows, but simply a subset that is good enough to develop a decent app. The idea is not to bring every great Mac app to windows but to provide a good enough windows framework to win developers and bring their current windows only apps to the mac.

It is actually good that not every app could compile for windows. The goal is simply to be better that what MS offers to provide an incentive to move to Cocoa and get the mac market for free.

We hope one day they become mac only developers as they discover the OS X only stuff!