I've never thought SF was about predicting the future, and I believe I've read my share of SF. For me, it was about two things: escapism at the soft end, and philosophy at the hard end.
I won't talk about the escapism, but the philosophy aspect is more interesting. Usually, it's about changing one or two things about our world, i.e. the present, and seeing how things play out. "What if" scenarios are briefly explored, poked and prodded. IMHO, short stories usually end up being the best format for this kind of intellectual experiment. It's a little like how study of history lets you reexamine your assumptions about the present, by contrast with back when society, communications, technology, etc. were different. It lets you examine the human condition: what changes with circumstances, and what stays the same. Good SF does similar things, but permits using imaginary technologies, societal arrangements, rather than relying on specific histories.
> "Current economic conditions rule out the possibility of past, present, or future time machines. The interest rate would always be zero if time travel were possible, because of the arbitrage opportunities that time travel would permit. Positive rates of interest are positive proof that time travel, unlike space flight, is pure fantasy."
There's a small explanation here of what he meant: http://www.robertgraboyes.com/writings_files/Bank%20at%20the.... His point definitely seems to be more intelligible after reading that article, but he seems to have a very limited definition of time travel. First, it must allow travel both ways. Second, one must be able to change the past. Third, the changed past must be the same as our past (Think of each new time travel instance as a new stack frame, with the stack variables being history. If one were to go back in time and change the past, one could create a new "stack frame" that leaves the history intact in its own timeline.)
However, one doesn't need a rather weak economic argument for the impossibility of time travel -- analyzing a light cone shows that causality will break down at speeds greater than that of light. Thus, traveling greater than the speed of light is equivalent to time travel. Using the Lorentz factor, we can trivially derive the fact that achieving a speed greater than that of light for a particle with finite mass requires an infinite amount of energy -- thus, time travel is impossible (assuming Einstein's Theory of Relativity is correct, which we are pretty damn certain about).
It's odd that an economist wouldn't mention transaction costs in his model at all. If the cost of time travel is extremely high, it wouldn't be worth it to travel back in time for economic purposes.
It's also possible that those with time travel ability choose not to alter the past for any of a number of reasons.
Further, by the point at which time travel is developed, money may not have any importance.
Yet another possibility is that our future may include a point of complete economic collapse in which all current banks cease to exist.
There are plenty of good arguments against time travel, but Graboyes's isn't as successful as he would like it to be.
Funny this article refers to hard SF, but does not mention the branch of SF into which econonics fits: soft SF. And some soft SF writers, like Le Guin, do have a strong background in social sciences, and do write things that at least glancingly cover economics.
But the best example I can think of is Barnes's _A Million Open Doors_, set in a world that has just been exposed to a disruptive new technology. The resulting crash of its markets is a central theme of the novel.
I'd say the opposite: hard SF needs an underlying economic model for it to work, because the protagonists are necessarily resource-constrained. Alastair Reynolds is particularly good at this: in his universe, interstellar travel is possible using a combination of relativistic time dilation, suspended animation and various therapies and enhancements for longevity - there's no FTL. If his characters have to go get something from another star system, they have to sit down and think, well, is it worth it? And it will take X years anyway, so let's spend a few years getting ready.
Star Trek even had to abandon any concept of economics because there's no viable model for it in their soft-SF universe but even so: the Federation's resources are finite. How do they decide what planets to colonize, how many starships to build, who is the poor schmuck who fixes the replicators?
I won't talk about the escapism, but the philosophy aspect is more interesting. Usually, it's about changing one or two things about our world, i.e. the present, and seeing how things play out. "What if" scenarios are briefly explored, poked and prodded. IMHO, short stories usually end up being the best format for this kind of intellectual experiment. It's a little like how study of history lets you reexamine your assumptions about the present, by contrast with back when society, communications, technology, etc. were different. It lets you examine the human condition: what changes with circumstances, and what stays the same. Good SF does similar things, but permits using imaginary technologies, societal arrangements, rather than relying on specific histories.