&quot;I don&#x27;t even know what kind of programming those languages aren&#x27;t a pain in the ass for.&quot;<p>If we limit the discussion to ML languages, they are generally very nice e.g. for datastructure transforms (including interpreters and compilers). Static typing with  type inference makes implementations short, and, if written in good style, are correct when they compile.<p>There are various other reasons why one would not want to use them. For me it&#x27;s platform stability and availability - while I enjoy functional languages <i>in principle</i> - I yet seem to choose C++ more often than not for my hobby projects.<p>I would say learning self-described fp-languages have made me a better programmer who values static typing more than before.