Fictions are introduced, as a logical system, for the purpose of making a world logical.
By introducing a logical system, we become able to say "true/false", "right/wrong", "good/bad" in a real world, which is by itself transcendent from "true/false", "right/wrong", "good/bad".
A fiction is what we artificially make for the purpose of making a world (a being/matter) logical.
Introducing a fiction is introducing a logical system.
A fiction is required because the world is not logical by itself.
"Logical" means "computable", in a broad sense.
The significance of logical system":
Rule under which we compete
We compete under a rule to decide who is "right/good/superior".
We apply a fiction to a real, create a fiction, in various situation, and by various reason.