As in, there are a handful of large projects the languages are used for. For Haskell, Facebook's spam detection system, Sigma[1], comes to mind, along with some use by banks (Standard Chartered); then there's a bunch of smaller places using Haskell (Wire, a secure messaging app, like Signal; Galois, a US defense contractor doing software verification and related things) plus some open-source tools like pandoc.

I know less about OCaml, but at least Jane Street is using it.

It's somewhat niche, but it's not like it's only used for hobby or toy applications.

[1] https://code.fb.com/security/fighting-spam-with-haskell/