First, he told MTV Multiplayer, "Nintendo has always been at the forefront of active gaming." He cited the Pokewalker, Personal Trainer: Walking, and, of course, that whole Wii thing. Second, "it's just another reason to encourage people to get up and walk around. Why? Because we want them to be carrying their Nintendo 3DS, going through StreetPass, SpotPass types of activity."
Apple managed to get people to carry their iPhones around everywhere by making the iPhone a phone -- one of the major advantages enjoyed by that platform. Nintendo has chosen to basically bribe users with virtual coins in order to get people into the habit of making the 3DS part of their everyday equipment. Hear Reggie's explanation for yourself in the video after the break.