The library was a part of .NET version 4.x and was then dropped when Microsoft wanted people to move to Azure.
We had similar issues with the AD APIs in .NET. You’d think Microsoft would have extensive AD integration support for C#, but you’d be wrong. It’s nothing you can’t fix by overriding the standard libraries with extensions of your own, but it’s a lot of work. Which is kind of the opposite of why you’d pick C#. At least in my opinion, you pick it because it comes with a powerful IDE and powerful standard libraries, but it turns out that it doesn’t actually do that once you dig a little deeper than standard CRUD applications.