Hunh? C# was one of my first professional languages and I used it for five years. It's an excellent language and many people use it. What 'grain' do you think you are going against?
The more platforms and languages you get exposed to, the more informed choices you'll be able to make in the future.
The .NET community is extremely large, perhaps you run in a small circle.
A job search on indeed.com (a job listing consolidator) within 25 miles of my area, Santa Monica, CA reveals
2,477 jobs for .NET
2,083 jobs for Java
1,284 jobs for python
685 jobs for Ruby
Here are # of questions with following tags on StackOverflow:
Java: 845,330
C#: 786,850
Python: 417,737
Ruby: 132,074
I can't speak for the rest of the world, but I would guess if you looked at 200 of the largest companies in Los Angeles, 90% of them have at least some .NET code running for something. It's pretty ubiquitous.
Damn would I like to live somewhere that has 1284 Python jobs listed, over here in the UK .Net (outside the web) dominates, love me some C# but Python just isn't on the radar at all (yet it's widely used internally).
Not everyone is a web developer or working on mobile apps.
Games and business software are two huge industries which are almost entirely Windows. Everyone using the massively popular Unity engine is a C# developer.
The more platforms and languages you get exposed to, the more informed choices you'll be able to make in the future.