At first, things like page numbers, indexes and contents pages didn't exist, but publishers soon adopted them because they work. Indexes aren't sexy. If you are writing fiction, you don't need an index. Book designers, every bit as creative as Web site designers, don't complain about having to have contents pages and indexes, and they don't see book navigation as a chore or a restriction on their creativity. The problem with the Web is that the navigation is always in your face.
Every page has the whole navigation structure on it, over and over.
It's like printing the table of contents of every subsequent page of the book. So people feel it more keenly if they don't like a Web site's navigation than if they encounter a poorly designed book index. The reason for the ubiquity of navigation elements is that the Web is still low-bandwidth. With a book, it's easy to flip to the index and then go the page that mentions naked mole rats . Clicking on the sitemap means an extra page load, and it is likely to be a long page.