As generous as the act is, it is in his nature to wonder a reason. When you're in the business of deals and trades, it's only natural to apply it to everything in life. This act of kindness doesn't benefit Rook, so why should Jade believe it as something so simple? While he's accepted small trinkets and gifts from Rook before, it has always been with some level of equal exchange in mind. Even if Rook hasn't asked for anything yet, it doesn't mean that Jade hasn't already decided what he'd be willing to offer in exchange for each one.

"Why would I not? Nothing in life is free. Where I am from something like this would be worth something quite considerable." Food is always a valuable resource... even if less than perfectly edible. Potion ingredients like these can potentially be even moreso.