I think was hit it, but here's how I'd put it:
BECAUSE THEY DON'T KNOW THAT IT'S LAME.
Seriously, most people producing science fiction these days simply don't know science fiction. They haven't actually read science fiction. They're not familiar with the tropes, the cliches, why sf fans like it, or, really, anything about the genre.
They can't even tell when something is incredibly lame. For that matter, neither can a huge chunk of the audience. And geeks, it seems, will tune into any sf, like dogs to bacon.
Here's to quality SF like Battlestar Galactice making it obvious to the average viewer just how lame this stuff is (and BSG isn't even very scientific... but it's good!).