The great thing about Sanji being an NPC is how his flaw can be used to justify any minion-like duties the players make him do on their behalf. Wanting to impress Nami - or any pretty lady in the vicinity for that matter - is a good internal motivator for Sanji that doesn't make the party seem like irredeemable douches when they make him do all the uninteresting stuff they can't be bothered to do. An NPC follower having a crush on a player character and wanting to get their attention by going above and beyond the call of duty (without making the whole thing uncomfortable to the player of said character) is a neat touch that can go a long way in giving the NPC their own voice and personality aside from just being a paid mook.

So it’s not just Rika he does that to, huh? Makes sense. In fact, he probably isn’t even consciously doing it - I’ve heard that most manipulative types aren’t actively setting out to manipulate people, it’s just something they end up doing when they try to “win” every social interaction they’re ever involved in.

Admittedly Rika actually did say she would stay inside where's it's warm.
First time HE said anything though.