1) People got burnt out on spaceship shows.
2) TV series generally became more diverse and interesting, with more shows breaking the lawyer/doctor/cop mold, thereby making traditional space shows less special than they'd been before.
3) Advances in CG and other tech, along with growing budgets, meant more and better location shooting could be done. Consequently, spaceship/space station sets began to feel more cramped and dull than they had before.
4) As society became more and more demilitarized, military-ish sci-fi dramas began to feel old and musty to many.
5) The
LotR films and
Harry Potter began to tip genre interest toward fantasy, perhaps aided in part by a subconscious desire for quaint and simpler things post-9/11.
6) The sinister belligerence on top of deadly incompetence of the Bush Administration meant that narratives about heroic government fleets weren't quite so appealing anymore.
7) After 9/11, and given the appalling sectarian violence in Iraq and elsewhere, fictional squabbles about mostly white actors with simple makeup and prosthetic facial ridges began to seem both tame and inane.
8) People started to realize that there's just not much more to the solar system to explore. The moon is the moon, Mars is cold and barren, Pluto might not even be a planet. Ergo, spacefaring narratives lost a bit of their lustre.
9)
Enterprise sucked toes. Big, smelly toes.
Just some points I brainstormed up... take your pick.
