Actually, the majority of people diagnosed with a dissociative disorder have a trauma history. Dissociation is a continuous spectrum, but the more severe dissociation is clearly associated with trauma and abuse. While non-abused people can "lose themselves in a book, daydream,etc" they do not develop full blown disorders where space and time are altered to the extremes.

In fact, DID, is 100% associated with severe abuse. There are no known "true" cases that are not trauma related.