Do you want reasons? Here are a couple from someone that has learned ML with Caml Light, and most of the latter ML variants.
VS Tooling lacking versus C#/VB, no support for code generators, no support for Roslyn, no support for GUI frameworks, no support for EF tooling, many .NET vendors don't support projects if using F#, community likes to create their own wrappers instead of embracing standard .NET projects, ....
For whatever reason, C# devs seem incredibly resistant to even just looking at F#.