[Odd musings alert!] What does fiction do? Sci fi?(also on predictive abilities thereof)

This might be more of an attempt to fish for a discussion than anything, as I'm not sure I have the answers.

If we are to assume the job of fiction isn't merely to provide entertainment (not that there isn't a place for such books, I'm just saying that the great books that stick in our memory tend to dig a little deeper and can come with a non-formulaic structure). Rather it's to bring into focus or to light an aspect of humanity. In general what's the best vehicle to conduct this? Amazing characters and stories? These definitely play a role. But what about Sci-fi? This genre tends to be overlooked by some, but it can provide a great vehicle to ask questions about today by making the reader suspend his or her belief in the world and slowly draw the parallels.

But then what of the those predictions in sci fi? Surely some are made concerning the politics and the technologies? Less so with characters. The interaction between the people and the new world usually makes for interesting outcomes (and the answers are revealing)... But these predictions usually take the form, at best, of linear extrapolation of a system that needs complex models. Is there any other way to do it? Wouldn't anything else be more complex than readers would care to read? And if it does make for good reading, shouldn't there be a program to help with these complex interactions? I see something else that computers will possibly be better at some day.
Thoughts?