Being in customer support I often experience the exact opposite. We often do not know how to explain stuff so that really nobody will misunderstand. I've recently summarized this as "everything that can be misunderstood, no matter how remotely, will be misunderstood" even little things like "click this, then click that."

We have an App (of debatable quality) where we made screenshots with big red circles so people know which button to push, as many do not read the button's label.

Sure, I also misread email. Easy enough to say "sorry, my fault" and fix the problem.

EDIT: As this might sound very negative: the whole situation is more like "collective creativity", rather than stupidity. I'm often astonished on how people think and what there reasoning is. Ways of thinking I'd never imagined. And no matter how absurd, there's always some logic reasoning.