It is interesting to see people call an image a "cover" and a website a book even when the said cover actually never covers anything nor there is a book in there because a website.
PDFs and Word were originally designed (still meant to) for enterprise documents, not books. It works somewhat for books too but then PDF is not really "on web". People still have to download an artifact, save it somewhere or may be bother about other similar digital book formats the same way.
Why, viewing content on some god forsaken web site, page by page, through some proprietary plugin, with no ability to save other than taking a screenshot of the window.
