Take the Force Protection green bubble from the Jedi Knight games, or the glowing purple hands of the flurry animation in KotOR. Anyway, I guess there's some unwritten rule in LucasArt's development bible that says there have to be shiny special effects even if they don't make sense.
Also, for some reason I'm talking like Andy Rooney. Ever get annoyed by some of the visual effects in Knights of the Old Republic? I know I have.