If they aren't your kids, why would you care?
Other people and their children are of no consequence to me.
Simplest answer? I'm not a sociopath.
Neither am I, but other people's children are their responsibility, not mine.
Parents have a right, within the existing laws, to raise their children in a manner that they see fit and I'm sure as hell not going to get involved unless I think that the child is in imminent danger.