Edit: these developers know damn well if their target demo is children, and they know damn well that the phenomenon of children running up huge debts without the informed consent of their parents is all too common. They know what they're doing; they can't plead ignorance. At best they are self-deluded, but it's more likely they are morally corrupt. Blinded by their love for money, totally indifferent to the suffering their business model causes.
It's absolutely revolting, and so is anybody defending it by implicitly asserting that it's okay for developers to exploit children if their parents happen to be careless or neglectful. "The parents are to blame for allowing it" does not absolve the developers who knowingly profit from it. Should it be legal for me to sell cigarettes to a child if their parents were foolish enough to give the child a credit card? Of course not, fuck off with that shit.