When you write on a piece of paper your eyes can scan down the discreet print format, jump to headings and paragraphs, turn pages, etc. The document is readily accessible, and our eyes have been trained and have adapted to paper as the medium. It is different for a computer screen's monitor. Small type is difficult to read because of the resolution of the type's display.
Sentences fill the width of the monitor, and often are too wide.
The writing style differs. This may seem like a superficial treatment of subject matter, and it can be. However, keep in mind that millions of websites compete to deliver information, and if your website is written in a clear, direct manner, you will succeed in delivering information. Interminable text goes on and on demanding perseverance to get to the good parts. Rather, the web can be a very effective way of delivering information that is printed , and then read.