I never understood Apple's Marketing. By allowing non-OSX users to install whatever OS they want, they can only increase sales, even if it means providing drivers. I think we can all agree that Apple's biggest forte is hardware design.
I'm not going to criticize OSX because it serves it's purpose, but it is by far the most limiting factor of Apple gear in general aside the price. In comparison, Windows 7 has become the workhorse of the corporate desktop world and I can't see this as anything else than Apple being snobby.
This is one of those situations where Apple should keep supporting it just because it can for the benefit of the people who might potentially buy their machines. Apple purists are ok about spending $3000+ for a desktop that in reality should cost half that. When you are trying to pull new customers into the fold, the last thing you should be saying is that you don't support the number one corporate desktop OS in the world.
Of course I'm aware that companies who buy Mac Pros are likely OSX users and that in the long run it doesn't change much. In spite of that, even if 1 out of 10 machines was purchased by someone who plans to run Windows 7 on it then the profits would be enormous based on their pricing scheme. At least, certainly high enough to absorb the cost of updating drives.