The page, which ever way we look at it, has quite strict dimensions.
Words and sentences, which ever way we look at them, also need a rather strict formal linearity.
Combined, we develop books that privilege a beginning, middle and end. Our dominant forms of fiction, and academic writing, strongly support this model.
On the other hand many of our works also provide mechanisms to counter this linearity tables of contents, indexes and footnotes are all various ways to provide alternative pathways through a text.
Hypertext is able to make these alternative (and apparently lesser) pathways central to the text itself, so no longer does a work require a single and dominant centre, but can actively allow the reader to meander through a field of work.