Ray Bradbury on What Sets Science Fiction Apart

"[T]he mainstream hasn’t been paying attention to all the changes in our culture during the last fifty years. The major ideas of our time—developments in medicine, the importance of space exploration to advance our species—have been neglected. The critics are generally wrong, or they’re fifteen, twenty years late. It’s a great shame. They miss out on a lot. Why the fiction of ideas should be so neglected is beyond me ."

-- Ray Bradbury from a Paris Review interview (initially earmarked as “a bit informal in places, maybe overly enthusiastic” but isn't that part of the charm?)

Not always true, but generally.  However, literary works tend to focus on the life between the details, which SF generally doesn't do (not always true).