ONE PIECE GOLDD: In chapter 653, when Shirahoshi and the crew promised to go on a walk in a real forest the next time they met, why did Zoro and Franky not do the pinky promise?! –Yuminami Kobayashi Cat
O: Hmm… seems like many people were bothered by this. There’s no real deep meaning to this, but based on the path the story traveled and the individual characters’ actions, it seemed like maybe those two in particular hadn’t had much interaction with Shirahoshi, so why would they feel the need to hold out their pinkies? Of course, given that their captain and crewmates made that promise, I’m sure Zoro and Franky felt just like the rest of them, don’t worry.
I think because they two feel like “adult” so they acted cool and doesnt do child-like things, but they felt like the rest of them.