The reason why this happens is Jim gets Annie to write his backstory. he comes up with the idea of his scoundrel with a blaster, and has annie fill in the blanks, "So he has a rich character background" But of course he never reads it, since its only there for him to not die quickly. So the dm keeps grabbing stuff out of this quite frankly awesome back story and uses it as plot hooks.

Of course, all this is assuming the characters are even relatively close to canon. Remember darth maul the detective? Darth tyrannus the guy trying to expose the evil emperor? Greivous the batspit crazy cyborg? For all we know, Jabba is an old friend of the family trying to help them all escape, lando is the hidden sith apprentice, and greedo is trying to track down anakin to get revenge for his little brother that died all those years ago, and thinks luke is the link he needs to find him.