I think its the basic philosphy of letting the older kids look for easter eggs last. You hide the eggs and let the little kids go first. They quickly pick up their share. Then you send out the older kids. They spend the rest of day trying to find whats left. While both ages may have the same amount, its a whole lot harder for the second group to get theirs, especially if the little kids decide to take a little more than their share. Its all about extending opportunitiy.