TLDR: C# is our real language. F# is a thing that gets supported to the extent that unpaid volunteers do the work. VB is in back-compat legacy support mode.
Huh? F# has Microsoft Research building it and its libraries and optimizing compilers, no?
C#
>We will keep evolving C# to meet the changing needs of developers and remain a state-of-the-art programming language. We will innovate eagerly and broadly in collaboration with the teams responsible for .NET libraries, developer tools, and workload support, while being careful to stay within the spirit of the language.
F#
> We will drive F# evolution and support the F# ecosystem with language leadership and governance. We will encourage community contributions to improve the F# language and developer experience.