The problem is that people who are drawn to F# tend to be a certain kind of people: generally stronger in CS, but also more prone to think that changing programming language is a solution to a wide variety of problems.

Many people are not like that, and stuff like a small community, worse tools and toolkits and less programmer availability are actually a huge deal, capable of tanking a good project, whereas having a 10% better language isn't a huge gain.

It's that simple.