I think this happened as a result of almost every single piece of EU lore trying to be "iconic" . SWTOR included, they diminished everything unique about the movie characters because "HEY GUYS LOOK THIS HAPPENED IN THE MOVIES AND IT HAPPENS HERE TOO ARE WE STAR WARS YET?" .
That's one reason. Another is that untalented and unoriginal writers cannot make it attractive by great storytelling so they get attention by crapping on OT. For example they make their characters more powerful than the most powerful in the films or use the unique concepts from the films and make them common. Take a look at the Force Unleashed crap (imo the worst SW game ever made) where this random moron (Starkiller) beats both Vader and Sidious. It is insulting to OT and its characters. Or the ridiculous cloning of Emperor in Dark Empire. Or equally ridiculous almighty 1000 years old Sith Emperor in SWTOR.