A close friend of mine asked me the other day why I "waste so much time" with fiction. Watching movies set in space, reading books set in improbably ancient times, writing stories covering both scenarios. Why do I "waste so much time with [my] head in things that will never happen."
Fiction, both speculative (read: sci-fi) and otherwise, is by far my favorite genre for storytelling.
I enjoy science fiction because it gives me a chance to look forward to the future and imagine what different things will be like as days go by. On the one hand, you could argue that I will never see frequent space travel or walk on another world.
Considering how much of today's technology was inspired by tales in the realm of science fiction, though, you could also argue that imagining a future I want is the only way that future will ever come to pass. I studied science in college, so I can usually tell how realistic a piece of fake technology may or may not be - the better the pseduo-science, the more likely I am to escape into the story and really consider the ramifications should such technology exist.
Fiction also presents the unique opportunity to reflect on current events or current disagreements without calling out the event or disagreement explicitly.
A college professor I highly respect used to carry on conversations with a large stuffed penguin during his lectures. He wasn't crazy, but he did like to crack jokes during class to keep everyone attentive. A few complaints early in his career about the unintended offensiveness of telling jokes directed at students led to the giant stuffed penguin solution - no one ever complained if he accidentally insulted a stuffed animal.
In fiction, you can delve deeply into highly controversial issues without anyone getting upset that you're discussing the issue in the first place. Battlestar Gallactica covered economic issues, social equality debates, racial politics, and a plethora of issues that would have killed any other show quickly - Gallactica threw in a bunch of robots, and that made the conversations OK.
I enjoy fiction because it provides a safe route through which I can consider both the future and the present.