I know a large number of pleasant, well-behaved, cooperative, and motivated kids and adults. None are motivated by fear of punishment, corporal or otherwise.
What are children for? Why have them? They need a lot of looking after. They are very expensive to keep and the costs go on for years and years. They can’t easily be given away and they can’t be “put to sleep” if their or your life becomes intolerable. They are very much less compliant than other companion animals. Often, they serve no useful purpose. They feel this lack of purpose and behave accordingly.