Most people's brains aren't trained for reading things properly unless it's with the intent of immediately applying what they read. They can try really hard to read carefully, but their brains are simply not in the right mode to absorb the material the same way they would if it were being put to use. It's hard to even become consciously aware of how poorly you're learning, because it feels like you're really concentrating.

I've finally gotten to the point where I can tell when my brain isn't learning like it should, but I still can't just will that mental state away.