Obviously "better docs" would be better for the users of software, but most people contributing to most open source projects (or indeed to most non-open source software!) are not doing so primarily for the altruistic goal of making users' lives easier. So the default position ends up being "do the stuff you find fun" or "do the stuff that your employer cares most about" or "do the stuff that fixes problems you personally are running into", which will often not be "great docs".
(I speak as somebody who's involved with an open source project whose documentation is overall not all that great and which doesn't have a "new changes must have docs" rule, so I don't mean to throw stones here -- just trying to argue that you should probably expect that poor docs are the norm and good ones the rarity.)
It's a bad example.
> If you want to try FreeBSD just use the Handbook, it documents FreeBSD very well. That said betrays childish aspects e.g. they refuse to list that FreeBSD can run on Linux/KVM (the mere fact it can, I'm not talking in depth instructions).
(from id=32369189#32372408)
https://docs.freebsd.org/en/books/handbook/virtualization/
goes way back... (and into the contained bug report)
https://forums.freebsd.org/threads/please-give-some-ideas-ab...