We regularly believe that, because we know, everyone else knows, and that's a failure I'm extremely guilty of. I gave my sister a Qnap NAS about 6 years ago and told her to just plug it in, plug in the land cable and set it up. 2 years after that she calls me asking for info on a data recovery service for her Mac. So I asked her why she needed data recovery, that's what the NAS was for. Well, she did what I told her, but never configured backing up her files.

So, yeah, now I assume everyone is ignorant and pass for arrogant some times over explaining.