Think about those download websites where you have to find the download link in the middle of all the ads that are masquerading as download buttons. There's a lot of information on those pages, but people become really adept at spotting the real download button. The rest of the information gets ignored.
I think this is why some people insist on verbal communication when you're trying to teach them something. If they get a text guide then they will gloss over things and skip steps leading to failure. With verbal communication you're effectively there to keep them at least mildly focused so that they don't gloss over things.