So I think, just reading this thread, there there are a lot of misconceptions of FP's capabilities. Things like statelessness - Haskell, Purescript, et al have ways of representing state, and for optimizing recursive behaviour into constant space/time (they even have great abstractions and data structures that can compete with C)

The number one reason is that ultimately it feels too different, and Functional programmers tend to be terrible educators. So it all feels very esoteric. To learn a pure functional language is almost to start learning programming from scratch.

The secondary reason is the package ecosystem. Generally speaking these languages have a rough go at dependancy mgmt/build tooling (stack vs cabal and the lack of good, simple guides for their usage, and the same for bower(deprecated) psc-package and spago. The problem is that once the tools improve - the docs and guides are all outdated. Good reliable information takes more digging in these languages.

BUT it is achievable. These are perfectly serviceable languages that can provide robust, provable behaviors. And in the case of purescript, a strongly typed environment on the web.

The development processes are out there and there are folks writing full stack FP. (myself included). But as a whole, pure FP needs a lot more educational material in order to grow.