It's not entirely dissimilar to a family that refuses to take a loved one off life support now that I think about.
I'm sure there are plenty of organizations that would love to move away from Microsoft, but its just reality that they can't. They are too invested in it. It would take too much money, too much time and too much political will to make a change. It's not their fault, its not even Microsoft's doing, other than being in the right place (on commodity PCs) at the right time (the '90s.) It's just the way it is.
C#? I'd much rather use C# over java.
Office? What's the alternative there? Open Office? Come on Open Office is far buggier, less user friendly, less productive, and has far less features. Google Docs? Missing tons of features, not to mention it's utterly useless when I don't have a network connection.
Visual Studio? Again nothing comes close to the features, speed, and stability. Eclipse is the nearest competitor imo - and it's still trailing behind a long ways.
Conversely there are practical, real gains to be had by using anything other that Microsoft products, but getting a large company to make any change before it is absolutely necessary is almost impossible, as current events demonstrate.
What is missing is a catalyst, something of an "energy crisis" of software, which will put this to rest.