Language vs libraries isn't just about an expressive language to build in when you don't have a library. The likelihood of a library's availability also depends on the barrier to entry. An amazing language that isn't usable by biologists won't have many libraries that solve biologist's problems.

To your original point of being "surprised at how many data scientists and quants are ignoring more mathematically principled languages like F#, OCaml and Haskell," I'd much rather use one of those languages, but I'd have to build the foundations myself. Today, they aren't the right tool for the job. They don't have the libraries I need, which means I don't build further libraries for them, making other people less likely to build on them, so they aren't the right tool for the job tomorrow either. I'd say it's a network effects thing primarily.