Eh what? My last job was at a bank, not exactly known for having the most interesting tech. They had several teams that used Scala and I've seen a lot of job listings for roles using Scala.

Haskell and Prolog slightly less so but at my current job (mostly Clojure, which is even less popular than Scala and Haskell according to the stackoverflow dev survey) we do have one guy who prototypes stuff in Prolog sometimes.

In fact according to the SO dev survey Scala and Haskell are used by almost 5% of professional developers, almost as much as Swift which is hardly seen as a language with "effectively zero" commercial use. They also rank a lot higher in the salaries section than many more popular languages. And I don't know how recruiters think but if somebody lists that they know Haskell on their resume and are applying for a JS job I'd assume they can learn JS pretty quick.