It's harder to accept Luke and Leia as siblings if you spent 6 years wondering if he'll get to fuck her. I don't think anybody's disregarding a story point because it came after the fact, it's just personal taste about how it was handled. This isn't holy text, sequels are ignored all the time. When I watch Jaws, I don't think Scheider's son grows up, works at Sea World, and gets attacked by another shark. In 3-D.