Because Sci-Fi MMOs have all sucked so far (Score 1)

This has nothing to do with fantasy. It has everything to do with the fact that, so far, every science-fiction themed MMO has outright sucked or, at best, been mediocre. So far, there has not been a stand-out sci-fi equivilent to World of Warcraft. SWG should have been that game, but LucasArts chose the wrong company to develop it.

A science-fiction themed MMO can be successful if:

* It isn't just a failed fantasy MMO with updated graphics.
* It is accessible and playable by non-hardcore MMO addicts (single biggest factor in WoW's success).
* It is essentially fun to play and not a grind (a concept that appears to be completely alien to most MMO designers until WoW).
* It uses the primary elements that make science fiction in general appealing as its main focus and theme (space, aliens, blasters, etc.) in the same way that successful fantasy use traditional fantasy themes as their main focus (magic, monsters, dugneons, treasure, etc.). See SWG at release for an example of what not to do.