People who can actually get it up for fantasy and SF are . . .All three explain why I like SF/F. Who doesn't love rich characterization, lavishly created worlds, and fiction that addresses the great questions of human life? And thus why would you prefer reading stuff set in drab contemporary times and peopled with the sorts of folks you already know, if you could get all three, to varying degrees, in a single genre?
(a) [those who] see the unrealistic world created by the author as merely a means to the end of producing character-driven stories, or
(b) [those who] see the characters and their actions as a means to the end of telling a story about the cool fantasy world they've created.
[(c] the main constituency of (literary) sci-fi, people who see the unrealistic world created by the author as merely a means to the end of addressing present day social/philosophical issues.
Here's a rousing defense of SF from across the pond, where fantasy is respectable but science fiction seems "irredeemably adolescent":
“In a fantasy story,” Aldiss says, “there’s a big evil abroad, but, in the end, everything goes back to normal and everybody goes home to drink ale in the shires. In a science-fiction story, there may be a terrible evil abroad, and it may get sorted out, but the world is f***ed up for ever. This is realism. It’s certainly not beach reading, unless you can find a really nasty, shingly beach.”I disagree with this characterization of fantasy, and authors like Miéville and Martin probably would as well.
. . .
SF is, in fact, the necessary literary companion to science. How could fiction avoid considering possible futures in a world of perpetual innovation? And how could science begin to believe in itself as wisdom, rather than just truth, without writers scouting out the territory ahead? Which is why this widely despised genre should be read now more than ever.
. . .
But if new hard, logical, shingly-beach SF is now a rarity, at least there’s a lot of old stuff to read. The literary snobs will say it’s badly written, which most of it is. So is most “literary” fiction. Badly written literary fiction is, however, wholly unnecessary. There’s a lot of badly written SF that is driven by an urgent journalistic desire to communicate. That is necessary.