User blog comment:Enryuu2015/Straws Hat Bounty/@comment-30127592-20180503172324

I suppose it is because the raise was based on Morgans and Stussy's reports on the events on WCI, which can probably be summed up like this: Luffy attempted to assasinate BM with the help of Bege (poor Bege, shoved out of the limelight like that), The Vinsmokes, and Jinbe; causing a lot of chaos and destruction in the process. Since neither of them are aware of any special feats/involvement of the other straw hats, there's little reason to increase their bounty, though i do think it's odd there wasn't a general increase for supposedly and actually uninvolved crew members like in Dressrosa.

As for Sanji, it IS technically still his arc, so a bounty raise seems appropriate. It probably has to do with the government learning of his Vinsmoke connection, especially with the family's involvement in the assasination. And who knows, perhaps there's a strict government policy on huge wedding cakes Sanji unknowingly violated ;-)

It's definitely a shame to see the others' work go unrewarded though. I'd expected at least Nami, Brook and Jinbe to get a raise, but unless Oda has yet to reveal those increases, it seems we'll be left wanting.