I started off learning Scala in a 2 man band startup for 3 or so years and moving to a company with 20+ full time Scala developers was a huge eye opener. All the things that hooked me about Scala like taking advantage of its relatively un-opinionated structure to be quite expressive with how you build things turned out to be major pain points when you scale out into teams who rotate developers on frequent basis.

I think I'm paraphrasing something I read about Twitter when I say that everyone who uses Scala ends up taking a subset of the language they are happy with, and that ends up being the case at a team level and intra-person level too (starting at the new place ended up with some very frosty pair programming sessions).

Add to that the necessity to cross train every developer who joins because recruitment is hard enough without specifying experience in a relatively obscure language and you have a constant cycle of painful recruitment, on-boarding and maintenance.