As it turns out, the kid does not have to own the smart phone to operate it.
Consider this: you are a parent with:
(a) A smart phone
(b) a young child.
Now, you are hanging out with your offspring one day and he (its a son, ok?) expresses interest in your phone. Wanting to be a good parent and wishing to educate your child about the world that he is growing up in, you explain what the phone is, what you use it for, and how it works. Since playing with something is a better way to learn about it than getting a lecture on it, you let him play with your phone some. He opens and closes apps and the like. Seems like fun -- but does it have to only have boring email aps, he wants to know? No, you tell him, you can play games. So you go to the app store and buy a game called Smurfville (or whatever) and show it to him. He thinks it is cool and that is it. You just taught your child something. Congrats on being a parent.
Now, a few weeks later, one of the following things occur:
(1) Your child takes your phone from your purse and (since you were kind enough to teach him how it works) he opens Smurfville. Then he plays it some and is like, "Gee, wish I had some of these smurfberries that they are offering to give me..." And now you are out some money.
(2) You are at your friends how and you son expresses and interest in seeing you phone. Sure, you tell him, just don't make any calls (don't need him calling the boss do you?). Things then proceed to play out as above...
(3) You leave your phone out on a desk. Your son finds it...
(4) Your spouse/boyfriend lets you son play with your phone, since your spouse/boyfriend saw your son playing with it one day...
I think you get the point. In none of this scenarios does your child own a phone. However, in all of them you have just bought some smurfberries.
Perhaps instead of ranting against parents that they need to be aware of every little thing that their child is doing, we can just agree that life is complicated and somethings are nice not to have to worry about all the time? I mean, kids do stupid stuff all the time. Stupid stuff that costs real money. Good kids. With good attentive parents. Why wouldn't you take steps to help limit the potential for that damage?