One common excuse for fiction reading is to suggest you learn passive facts about the setting as you progress pleasantly through the story, but that's not a particularly strong argument in favor or reading fiction. Sure I could pick up a book about Austen-era England or I could read an Austen novel and get a slightly inferior product education wise with a nice romantic chaser.
That's not what I'm talking about. Specifically I think fiction is a way to learn though experience vicariously, and I think there are some things learned best and perhaps only that way.
For example I could read a terse description of objectivism or I could read a Rand novel and walk a moment in the shoes of her characters. I would argue that the chance of fundamentally understanding what her philosophy is about through channel one is very low, although it takes a lot less time.
Another example: I could say "Sentience is not mutually inclusive or exclusive of understanding" or alternatively read Speaker for the Dead. "Morality resides entirely with intent rather than result" or read Ender's Game. "What is self?" or read Down and Out in the Magic Kingdom.
The deepest and perhaps most important topics can best be addressed this way. Regardless of how you feel about the historical accuracy of the Bible or Qur'an, certainly someone found it valuable to tell stories and parables to covey abstract concepts.