When written well, manpages are an awesome form of reference documentation.
That often doesn't happen, though.
(Manpages do not need installation instructions or the full changelog for the program. They do need examples, including the simplest possible way to use the program.)
This reminds me, I've not taught anyone how to write manpages in years. Maybe I should?
https://liw.fi/manpages/ is hopefully still reasonably accurate.
@liw I personally use txt2man and there's scdoc
Lars and friends