"The system default is designed for the majority of the users, not for a specific minority subset."
Maybe you can answer my question. Stating how many CLAIMS Apple has is no indication of how many children (under 18) or parents own iOS devices that would determine majority/minority "settings" defaults.
I have no idea what larger point is being made here, but there were 28 million accounts that made an IAP in a game designed for kids. Even assuming every single one of them involved an unauthorized purchase by a minor, we are still talking about a minority.
(About 90 million iPhones, 50 million iPod touch, and 15 million iPads had been sold at the time.)
Hope that helps!