I think it's possibly because: * F# projects are difficult to setup and use in Visual Studio in conjunction with existing C# projects? * OO developers just can't get their heads around functional paradigms? * There aren't enough jobs around that require the skills so we're not incentivised to learn it except in a few special cases like finance? * Immutable structures just too hard to learn to work with effectively? * Not enough supporting libraries (e.g. Nuget) available for consumption and use in F# programs * Too hard to write for the web? * Monads are hard? Or a combination of these? Or none of these? Weigh in and lets us know why you think it is the case and what can be done to change it, or if it even needs changing at all?! If you have used it for production work - at what point did you become comfortable, and if you haven't, what's stopping you?