We are wired for individual rather than general insights. Stories are much more effective at communicating certain things than treatises are. I would never have believed, in theory, that a man who enjoyed killing could be worthy of respect; only a story could convince me. To use Robin Hanson's terminology, narrative can bring near mode and far mode together.

Why not true stories? I think there you get into Aristotle and why versimilitude can be more effective than mere reality. True stories are good too, but life is disorderly and not necessarily narrative. It's a truism of writing workshops and creative writing classes that whenever you see a particularly unrealistic event in a story, the author will protest "But that really happened!" It doesn't matter; it's still unrealistic. Narrative is, I think, a particular kind of brain function that humans are good at, and it's a painting, not a photograph. To tap into our ability to understand each other through narrative, we usually need to fictionalize the world, apply some masks and filters.