Mainly because users are new to Linux / Arch Linux / Manjaro Linux and have no idea how it hangs together. Sometimes it is related to poor Linux hardware support (ie nvidia optimus laptops).
Instead of internet seraching, wiki searching (Manjaro or Arch), or forum searching to try and gain a better understanding, they simply create a forum thread repeating a question that has been asked 1000 times before… “Tell me!”.
This kind of behaviour IMO needs to be politely phased out via stricter moderation, creation of sticky thread with links to common questions / issues, and a change in how the community deals with noobs and help vampires. Be polite, friendly, courteous … but also be consistently firm.
There is this ridiculous notion that Manjaro is noob friendly, it is not, no rolling release distro is. New users need to be reminded of this also.