Children can be more clever than non-parents expect.
Surely, you jest! This is Slashdot, where everybody except actual parents knows the proper way to raise children, and supervision means hovering over your child at all times, never bathing or using the restroom or cooking meals or sleeping.
I'm glad some commenters don't have children, although if they did, they wouldn't sound so high and mighty at times like this. Seriously, my six year old plays outside with neighborhood kids all the time and builds way cooler stuff with Legos than I did at his age, but having other recreational activities didn't stop him from getting his hands on my wife's phone for a few minutes earlier this week and spending $16 on in-app purchases before she stopped him. And that's all because we had the audacity to have an infant that needs more attention when we aren't rich enough to both stay home and hover over the children all day.
We're not going to be joining the class action lawsuit or anything, but it's tiresome to see armchair parents pretend like they could stop it happening. Like most of you we have a lot of devices around, and no matter how well you think you have everything locked down, all it takes is one mistake. This is the only time my son has "accidentally" spent money, and no matter where you want to lay the blame, consider this: if my wife had an iPhone, this wouldn't have happened. Is that really the response you think Google should give?