Reading seems to be a lost skill. I have several clients where this is an issue, if my email is more than a few sentances it seems they just stop reading, or can't comprehend with all those words and letters in the way.
For one project the client wanted to do something that wouldn't work, I explained during a conference call why it wouldn't work, I explained it in an email with an attached plan showing why. A week later I get an email back asking if they can do what I just explained couldn't be done. I ended up having to find a picture that showed the area in question, draw on it to show him that his idea would not work and email that to him. Keep in mind that this is in his plant, and he in 5 minutes he could have walked out looked up and seen what I was talking about. In house we have joked that we need to start randomly coloring words, using 40 point font, or only using the important words just to get people to read an entire email.