Zoro knew what was dearest to Luffy next to his hat, food. Which was why this game of catch was the most fun to play. Watching Luffy get childishly angry while he laughed was a highlight on any day. Sometimes he would lower it just in reach, but then quickly pull it up again just to get an angry HMPH in return. Sure Luffy could stretch to get it, but what would be the fun in that? This was their special game and despite how annoyed Luffy looked everybody knew Zoro's laughter meant all was well.