Why are the Vedic historical narrations not chronological?

Incidents mentioned in the Vedic literatures, such as the Puranas, Mahabharata and Ramayana are factual historical narrations that took place sometime in the past, although not in any chronological order. Such historical facts, being instructive for ordinary men, were assorted without chronological reference. Besides that, they happen on different planets, nay, in different universes, and thus the description of the narrations is sometimes measured by three dimensions. We are simply concerned with the instructive lessons of such incidents, even though they are not in order by our limited range of understanding.

Srimad Bhagavatam 1.9.28 purport