Why is it that instructional photographs in books about photography are of such poor quality?

I was at the bookstore today and I picked up a book on Digital Photography. I never read a book written specifically for Digital photography (only film) so I was browsing through it to see if there was anything I could learn. Just so happens that there were a few photos early on in the book showing how to properly hold a camera. all three photos had a depth of field much too narrow for the subject, the edge quality wasn’t very sharp, colors appeared to be washed out and the framing and composition were horrible. Not what I would expect of a book written by a photographer.