I'm just talking from the documentation writing perspective. If you want the reason why there's more guides that utilize the CLI - here it is.
No.
Let's be honest - the main reason is that there is no GUI for these tasks or it sucks ass. Good stable GUI isn't hard to document either and you don't even need screenshots. "Go to App Store and install Firefox from there" is sufficient provided the said app store is working, easy to find and well-designed.
As for the writing docs... I agree but it depends on the application really. The goal of writing documentation is not to create documentation itself but to provide the user with assistance to get his task done - now and in the future. When we are talking about stuff like server components installation then sure, CLI rules. For some other things - not so much.
Also CLI documentation is often VERY version and environment dependent. There are tons of broken guides just because some config moved, version number changed or some parameter was renamed (and not necessarily in your application).
@shuro
> Let's be honest - the main reason is that there is no GUI for these tasks or it sucks ass
Sorry, but this is just plain wrong. I don't even need to change the example, GUI for package management is basically a solved problem. There are plenty of package management GUIs, and most of them are good.
"Issue this command" is still more efficient to write.