If anyone gives you one answer and says it is the only reason, they're wrong. So, this is a non-exhaustive treatment.
The reasons for reading or writing Science Fiction include all the ones for other fiction: It's a pleasant way to pass a gray, rainy day. It provides distraction and amusement while going through unhappy circumstances. Reading is cheap entertainment. If you have straightened means, you can freely check out books from a library, or just let me know and I'll give you a copy of what I've published.
moon for ransom. Romances may develop between dashing Civil War cavalrymen and time-travelling maidens.
I've explored elsewhere the relationship between Science Fiction and Fantasy as well as two broad themes of Science Fiction. And all that applies to this discussion of why one reads and writes SF.
Science Fiction prophesies about the Future
future shock. If I were to describe a typical workday to my teen-aged self of the 1970s, he would say it sounds like science fiction--because it does. I have an iPod, an iPad, an Android phone and a MacBook Air. Maybe I'll get an iPhone for my birthday. These devices are marvels of technology and I love living in the 21st Century.
But SF is a false-prophet. We haven't been back to the moon since 1973. We don't have jet packs. We don't have flying cars. Nuclear fusion power is still 30 years away. (Meanwhile I've gotten a half-dozen robo-calls today from various skeezy outfits. What fool does business with these companies? How do they stay in business?)
Despite the unexpected course of development with less progress in aeronautical or nuclear engineering, and more progress in telecommunication and electronics, we get glimpses into what the future will be like and get to play what-if with ideas like cloned replacement body parts.
Science Fiction lets us play what-if -- with things
Earth to the Moon. But if there were, what would it be like to use one? Or suppose I had a device that would transport me from anyplace to anyplace instantly?
Everybody loves unwrapping a new toy on Christmas morning and then seeing what it will do. Geeks and Engineers may also take things apart to see how they work.
Frankly, that's what I like about SF. I like inventing stuff that doesn't exist. I like coming up with a plausible-sounding explanation for why you want to fly into the sun and why the hyperspace drive works better there.
Doing real science is hard and so is making things work. But it's a lot easier when it just has to sound plausible. This may explain why Science Fiction doesn't predict the future perfectly. Flying cars are plausible, but iPods weren't plausible even when Steve Jobs announced them.
Science Fiction lets us play what-if -- with people
Or how about the starship pilot who's been in stasis for 80 years and he's thawed out by his great-grandson who has the same apparent age? How does that family dynamic work out?
Let's suppose you can clone replacement body parts. Sure, there are people who need heart transplants, but look at how much more money is spent each year for boob jobs? There's probably a lot more money to be made in upgrades of a cosmetic nature. And there's not as much liability if the replacement breasts fail.
Or let's suppose someone invents a device that tells when a politician is lying, and also when he won't keep a campaign promise. We might be surprised by politicians' creative responses to this challenge.
How would wars be fought if we only let robots do the fighting? Would we have more wars or fewer?
Science Fiction lets us grind axes
Strangely, they never beamed down to the Planet of the Over-promising Santa Clauses, or Planet We-just-ran-out-of-other-people's-money. Do you think we should go on the Gold Standard? You can have enterprising spacemen from there show up to End The Fed.
But Wait! There's More
The reasons for reading and writing Science Fiction encompass more than what I've said so far. Ferinstance, I didn't say anything about giving you a good scare. So, tell me, why do you read or write Science Fiction?