Stories grow by accretion. Tales accumulate — like dust. The longer the time lapse, the dustier the history — until it degenerates into fables.
Pelorat said, We historians are familiar with the process, Dom. There is a certain preference for the fable. The falsely dramatic drives out the truly dull.

Chapter 17 Gaia section 5, p. 361 - The Foundation series - Foundation's Edge (1982)