Far be it me to side with others against Leia but allow me to explain. NO ONE KNOWS THIS because Leia didn't tell them that she had no relationship with Darth Vader. All they know is it turns out she's been hiding she's the daughter of Rommel the entire time and kept that a secret. It says that she's willing to hide a large part of her past and who knows what else she's hiding. Is she actually a Rebel or was she a Lumiya-style Sleeper agent the entire time? Is she actually Leia? Was Leia replaced with a surgically altered Imperial agent? Was Darth Vader secretly aligned with Bail Organa and entrusted her to him while he rose in the Imperial Court? Is Luke Skywalker actually a Sith Lord who seized his father's title? Is Leia? These are all ridiculous but so is the actual truth. Which no one knew.