I think the best argument is that there are a lot of small financial institutions (small referring mainly to the tech groups at them, that is, so you might hear that some big bank uses eg Haskell but really it’s just some group within their IB arm. I’m sure google has some Haskell around too), and often the kind of people they employ tend to like weird languages.

Plenty of financial institutions use lots of c++ or java and plenty use cobol too.