Why enterprises use .NET and C# technologies?

I looked for Senior Software Developer positions, and one of the things that I've noticed is that lots of enterprises look for people with experience with technologies such as .NET and C#.

I personally HATE Microsoft and their platforms. From my experience they take all the fun from developing by creating stupid compile errors with their stupid gigantic Visual Studio and buggy dependencies. Not to mention their ridiculous resources greedy and unsecured Windows OS! Also there are no healthy and independent communities around a their technologies. They don't open source much of their technologies so it would be easier to hack their tools, and harder to make security patches.

Why enterprises do that for themselves and for their developers?

Do you think enterprises will make a turn in this attitude?