Because you love using Microsoft's shitty technologies, but also want to be completely unemployable?
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F# making you unemployable is debateable, but I don't see what makes F# any less employable than most other FP languages. They have some niche applications that make it useful rarely, but when they're useful its a terrific tool for the job. F#'s ability to interop with the rest of the dotnet ecosystem positions it better than most functional languages for business usecases.
But .NET's CLR doesn't seem especially shitty. It's not awesome, I don't feel that RIIR urge when I work with C# and I probably wouldn't with F# either but it's fine, it's like Java again, or maybe Go or Python. It's fine. I don't hate it and that's enough.