We don't. We have a much lesser risk of brain damage when we're young. Kids have had half their brain removed when they are little, and when they grow up they are fine. You do surgery like that on an adult, and they are fucked.
Kids are way more resilant to all kinds of head trauma. Babies sometimes go without oxygen for minutes on end when they are born, and turn out fine. While anoxia like that would kill an adult.