This is targeted at children under 7. Kids have a tendency to break anything with moving parts. Clamshell hinges are just one more thing to get broken. This is intentionally designed to be a sturdy piece of plastic capable of standing up to the standard abuses of childhood. Kid waves around, the hinge flips up and down, kid does not have a good time. They've spelled it out clearly in the article, this isn't meant to replace your 3DS, it's to bring in the younger audience which has trouble with the existing 3DS. That's probably also the reason they removed the wifi switch and made it software controlled, so kids wouldn't accidentally hit it while playing a game and then complain about it.