Okay, but just imagine if Sabo was somehow able to get back to his brothers when they were still kids. I don’t know maybe he didn’t suffer from amnesia and Dragon returned to Mt. Corvo, whatever. By some point Ace decides to learn how to be polite. And Sabo is rolling eyes on him, because he hates etiquette (not that he remembers much of even most basic etiquette). But Ace is adamant to learn and puts so much effort to be polite and even tries to teach Luffy.
Sabo is rolling eyes and groaning when Ace is stopping to thank politely for something or the other or apologize to someone, when they are trying to run away.
Sabo is like “Dude, we are robbing people” and Ace is “no need to be rude about it”.
And Ace never really tries to make Sabo learn any manner once Sabo mentions how he hated etiquette lessons. What works for him does not need to work for Sabo. He still tries to teach Luffy… with mixed results.
Sabo thinks whole thing about being polite and respectful is so unnecessary, but he changes his mind after realizing that this polite biz really helps Ace to communicate with other people and it makes Ace happier. He himself never had much problems with communicating with others so he decides not to follow Ace’s example. He is comfortable the way he was.
Cheloneuniverse 