I think one of the best and unintentionally funniest worldbuilding aspects in Star Wars is the reasoning of why did Bail and Breha adopt Leia instead of having their own children. Leia is first established as the princess of Alderaan before she is written to be Luke's sister. So now we need to figure out how she got to Alderaan. She was adopted because she needed to be hidden and separated from her brother. Bail was placed there to be one of the only people who knew so there would be a reason why it was them who got her. They specifically wanted a daughter. Why? Because Alderaan is a matriarchal society, so they needed a princess. Why didn't the Queen and her husband have biological children? Because they can't. Why? Because the Queen can't have kids. Why? Because she got injured as a teenager and got her internal organs replaced and her body can't handle a pregnancy. How did she get injured so badly? She fell off of a mountain. How did that happen? She was climbing it. Why was the future Queen climbing a mountain in the first place? Because she needed to go through three challenges in order to inherit the throne and one of them required her to go through something physically impressive. Why? Because before that they just held a Battle Royale for all the heirs and the one left alive got the throne and they at some point figured out that maybe they shouldn't be doing that, actually. Oh, okay.
