As the gaming industry grows, so do game development costs. And with the millions of dollors involved in game development comes great risk. Why create a project based around an unfamiliar setting to all but Star Wars fans when you can create a project based in a setting familiar to everybody, fan or no fan?
It's all a matter of Lucasarts weighing up the risks of different strategies to determine which one would allow them to create as much revenue as possible. It's sad, but it's true.