Oh for sure, it’s definitely less common, though there are a number of other companies running it in production as well. This isn’t my first Haskell job, after all. My last job was also a similar size company and codebase. Facebook was even running it for a while for their sizeable abusive content detection system before that was shuttered due to company politics/policies (back when they were trying to do something about it at all).

But yeah, it’s not the first pick for a lot of companies, though I tend to think of that as a simple mindshare/inertia explanation than anything inherent to the language/ecosystem.