Really, if people read everything they'd never get anything done. They see dozens to hundreds of things marked visually as important that they'll do fine ignoring, every single day. Of course they often miss the one or two per day that they actually needed to read.
Then there's the way styles are so different, especially on the web. Horribly user-hostile. How does this site mark something as important, assuming it bothers in the first place? Who knows. And if I'm only planning to be on it for 30s, I'm not going to learn that.