I assume that this is the same issue that plagues the (mostly younger portion of the) dev community these days: there is a LOT of code out there that is simply not visible to us in the way that an NPM module is visible.
There is so much app code and systems code that none of us will ever see, and that is absolutely by design. It is not intended to be seen, and it is the majority of code written to date. It is fire-walled and private and intended only for those who paid for it.
I am FAR from fancy, nor am I an expert in anything, so don't mistake my tone, but I have never shown any of my programmer friends and acquaintances anything that I work on every day: they are all about Rails and JavaScript, and I work on enterprise .NET apps, diving deep into SQL every day. What I do is completely hidden from them, both because they can't imagine anything outside of their precious Ruby Gems and NPM dependencies, and because I have signed NDA's that could ruin my career if I broke the rules. My point is, I've worked as a professional app dev for 2.5 years and I have never built anything that was intended for general consumption, and I know for a fact that many of us, maybe the majority of us, do the same sort of thing.
None of this is to say that there are vast, massive, infrastructure-critical Haskell code bases out there in the rarified upper echelons of coding society. But of there were, most of us would probably never know about it, at least not first-hand.