Beenthere had made a good point about manuals being tough to write for "greenhorns" (maybe not the term I'd use, but close enough).
Even manuals, work instructions or procedures used within a company are written with the assumption that the user has some experience or background in the work at hand. That's not always the case, however, and specific training may still be required and documented.
Manuals written for consumers are "dumbed down" (again, not the best term, but apt) since the writers have no idea about the consumers' ability to comprehend them.
All in all, those manuals are as much to protect the manufacturer as they are to educate the consumer...good example is any manual for a firearm.