OCaml specifically is such an obscure language you'd have a hard time explaining it to most people who are software engineers.
Who cares?
Lots of financial companies, including some serious heavy-hitters like Bloomberg, use functional languages like Haskell and Ocaml. I suppose the blockchain folks are pretty enamoured with it too.
Plenty of big companies like Twitter use Scala, which is plenty functional.
Even on the front-end side: JavaScript was directly inspired by Scheme; TypeScript was hugely inspired by languages like Ocaml and Haskell; React and Redux's inspirations fall directly out of the functional programming community.
Rust, out of Mozilla, is also a descendent of the functional programming world; its compiler was originally written in Ocaml.
Just the other day there was a conversation on here about type-system enforced optionals. Almost every "modern" language has grown these in the past decade, often including monadic combinators to help minimize boilerplate. All of this comes from what ML and Haskell were doing as many as 30 years ago.
Speaking of monadic combinators: these are also frequently used in modern languages with async libraries to avoid what the JS community termed "callback hell".
TBH if you've developed software in the past ten years, it's unlikely you haven't been hugely affected by what the FP community has been doing, and it's not impossible that watching what they're doing now give you a glimpse of where mainstream programming will be a decade or more down the line.
Apart from HN / reddit bubble, not many people know about FP, and not to imply that's their fault. FP is still weird, difficult for mere mortals, and ivory tower elitism is holding some of its useful ideas back.
* Java/C# generics
* sealed interfaces and record classes
* pattern matching
* first-class functions with closures
* even type system itself (eg Python is gaining a type system)
* ...
The world of programming languages is converging, no matter how slowly, towards ML
Given that most HR departments still value having a degree, that is still quite a bit of people, specially if one extrapolates to other countries that share similar attitude to universities and HR hiring practices.
I also like OCaml because it is both imperative and functional, so I can use the best of both paradigms.