The reason for this are rules of Star Wars which would be broken as the shooter plays 30 years before events of the movie.
"On Star Wars, the one thing that we are adhering to, and I think this is part of our arrangement with Lucas and Disney, is you can't make a game in Star Wars that violates the canon of Star Wars. Meaning you can't take something from the future and bring it back into the past unless it's a reference."Nonetheless, they want to keep in touch with coming Star Wars movies in the future.