As Robinson mentions, and as should be obvious to most readers in the genre, modern SF writing is highly literate and aimed at the upper five percent or so of the IQ curve. Not only must a potential science fiction reader be able to digest long sentences and words, (which eliminates most readers of blockbusters), they must also have a decent grasp of certain science concepts and have a mind capable of extrapolation (judging by the way science fiction is sometimes sneered at, this qualification seems to be eliminating most English majors). Right now, the genre is much more sophisticated, cosmopolitan and literate than the more traditional "literary" fiction (which, let's face it, is not going through a golden age).
This is a good thing, right?
The problem is that readers do not want sophisticated, cosmopolitan and literate. Readers want simple prose and hard-hitting adventure. Most adults have not read anything from the Victorian era since high school, have never read Ulysses and are not interested in doing so. They want something easy to understand, something that will entertain them at the beach or on the daily commute. Something that takes the place of Dancing with the Stars as a brain-off excercise. So they turn to Mitch Albom or Robert Ludlum (TM) or James Patterson, writers who have turned the short-word, short-sentence, easy-to-understand concept into an art form, and who justly reap the rewards for having done so - these are all great writers in their way (even the not-so-recently deceased Ludlum) who know what their audience wants and give it to them.
Adult readers who do come into the genre will be more attracted to the Young Adult section of the shelf, for the same reasons. This is why the HP books sold so well, and it's why Stephanie Meyer is selling millions of copies. The Keep It Sinple Rule.
There are lots of people who would love to see SF return to its pulp roots. Back in the thirties and forties, SF mags gave the public its quick action fix, and people bought them in droves. Soldiers took them to war in their packs (try doing that with a Kindle). They were popular entertainment (you can tell because the moralists of the day would cry out against them). Try asking an average two-book-a-year reader to read an Alastair Reynolds novel. They'll hate it, not because it has no action (these things are full of stuff going on), but because the prose requires a certain amount of erudition and commitment.
So shouldn't the literati embrace the new, more mature science fiction genre?
No. Well, they should, but they won't. You see, most New York intellectuals (and countless wannabes in university towns everywhere) associate science fiction with Star Trek (and even those of us in the genre have to admit that it was fun but not particularly intellectual) and have no interest in reading mind-numbing tripe of the same type. So they don't even bother (of course, they aren't very bright, so people like Margaret Atwood can fool them into thinking that The Handmaid's Tale isn't science fiction), and science fiction is excluded from the major awards which is a pity because most modern genre work would walk all over most modern literary work, at least from the point of view of the quality of the writing.
Perhaps it's time to be a little more assertive. Most people in the genre read extensively outside of it. I know I do. And, to tell you the truth, I really don't see much out there that comes near the consistently high quality I see in the Year's Best Science Fiction collections, all I see are boring rehashings of thiings that have already been done, in ever more tortured prose. The genre might have lost the casual reader, but we're certainly putting out better literature than the literary press - so why not go forth and sweep the awards?
It's time to leave the ghetto.