My favourite example of this was when we had an old PC that always kicked out the cd drive when it was booting up for some reason. This loud mouth sales guy who only only came in about once a week sat down and put his cup of coffee directly in front of the cd drive “you need to move that or it’ll get knocked over” I helpfully told him, explaining why. He said “oh right, thanks!”, turned back to the computer powered it on, whereupon the coffee was sent flying everywhere. He got very angry at this, loudly shouting about his terrible plight and pulling the computer’s power lead out in a fury (??) before retiring to the kitchen to make a replacement cup. On his return he put the cup in the exact same place, re-plugged in the computer and the exact same thing happened again.
I was just staring at him in disbelief that anyone could be that stupid.