Books are literally bound, held together between covers. Such works have definite endings (even multiple endings are endings).
A hypertext doesn't need to end. Endings are possible with hypertext, but not necessary.
A networked hypertext can link to anything within the network. Some literary critics (Burbules, Landow) refer to the trope of "catachresis" (far-fetched uses of a familiar word) as being a defining trope of hypertext.
But unless the hypertext is specifically constructed to lead to a pre-determined ending, there's no guarantee that a reader will find the ending.
A literary hypertext does not have a predetermined goal. If you read a literary hypertext looking for the hidden treasure, you're going to get very bored and frustrated.
Hypertext was developed not as a way of telling stories, but as a way to present information which didn't have or need a set linear arrangement: Instruction manuals, help guides, and the like.
But now that we have the Internet, hypertext can become even more radically unbound.