To suspend your consciousness.
To draw you out of yourself.
To give you knowledge of what other people are like.
To present philosophical ideas in literal, practical ways.
To teach you that time cannot be recovered, that no-one can tell you where past times are.
To make a higher art of gossip.
To escape, but into something bigger, more real.
To adjust you to living.
To warn you about taking dreams too seriously or wandering off into the woods.
To ironise behaviour that won’t listen to condemnation.
To talk subtly to some readers and generally to all.
To understand how certain groups of people act in certain situations.
To apply the lessons of social science to normal life (irrespective of how much social science the novelist knows).
To create characters more complicated than us.
To persist after death.
To detrivialise.
What else?
To entertain you
To demonstrate how others overcame (generally psychological) obstacles
To expand who are able to sympathize/empathize with
To challenge presumptions; to reveal virtue and vice and their consequences