Gregory's Server
@masukomi I semi-agree there. Of course writing a manpage for an image upscaler that does not have a command line interface would be silly, but for documenting config formats and switches I've found them incredibly valuable. Apart from being easy to search, they can be significantly more thorough than a –help text ever could and having them available offline certainly has its advantages for things like DNS resolvers. For examples, a markdown wiki (of whatever shape) can be a useful resource.
@masukomi and bad documentation comes in all flavours, unfortunately. I even have a list in my bookmarks, I call "documentation hell" and manpages are a rare occurrence on that list.
Whether I would agree with the first statement I am not sure either. Many programs come with switches that alter the programs behaviour (think proxies in chromium). Calling them irrelevant is ignoring the reality that is daemons and other non-interactive programs.