"I think it was just for the benefit of the patient population in general." Sai tilted his head, having thought the answer would have been obvious. Still, it wasn't Usopp's only reasoning, so he'd give Shikamaru that.

"He's something of an inventor, I believe, and possibly chemist. He was probably interested in knowing what would be of use to them." Then he paused, reminded of something. "And I believe their crew has a doctor as well."