Any game that can't create its own universe in Star Wars won't get good attention. Without stormtroopers, the majority of the consumers might not recognize what it's all about.
The genius of Bioware and the requirement of RPGs in general is immersion and exploration of a new universe. An action game doesn't make you travel as much and there is hardly enough time to properly immerse yourself, considering they don't last longer then 10-12 hours these days. Starting from a well known setting allows them to immerse the player from the start, without the need of an introduction into the universe.
KotOR, the universe, is not popular enough yet for non-RPG games to be based around it.