The big one for me is a practical one: the current ecosystems around them. I'd love to code mobile apps and web apps in OCaml but it would just be going against the grain too much for it to be worth it in the vast majority of cases I think. Can you easily deploy on most cloud services? Are there good libraries you can use? Is there a community that can help you when you get stuck?

It's not a fault of functional languages but that is the issue, it's that the vast majority of coders and ecosystems are entrenched in imperative languages still.

I'll use strong static typing where I can though e.g. TypeScript is decent in terms of practicality.