This is a problem that is very well suited to Haskell, but it is a subset of general software development. Here it is worth the substantial overhead of making robust types as independent teams are making rules for this spam filter and typing can enforce order on it as they are probably easily categorized by type of filter. There are also quant developers that enjoy writing in OCaml, and AI devs too. But besides major companies using statically typed languages for some special teams, we don't see companies switching wholesale. Like I am still waiting for the day where $bigCompany says "we have hit so many type problems in our code that we have decided switching to staticaly typed languages will save us tons of money and are now requiring it".
https://code.facebook.com/security/fighting-spam-with-haskel...