I'm not saying .NET developers will never use other libraries as an alternative, but they wont invent wheels (or used reinvented wheels) where the .NET provided one is solid. I am speaking generally of course. And there are many developers who are .NET + something else. I'm .NET and dabbled with Haskell and Node JS for example. I'm looking at Lisp as it is interesting. But let's write a web app in .NET. How many .NET developers will think "which framework should I use?". That is a valid question in JS/Haskell/Lisp. It's quite interesting, and its a positive for .NET in many ways. You can get stuff done, and also come in on a project and it be familiar.