Parents are regulated as to how they discipline their children. Spankings that were the tool of choice in my day are now illegal. Spanking is considered child abuse and can result in state seizure of the child and prosecution of the parent.
The state prescribes the terms on which children can be transported in cars. The cars themselves can only be designed within safety and fuel economy parameters determined by the state.
The unsupervised children at play of my generation no longer exist outside of small towns. Not that long ago I reported on the arrest of a mother on the grounds that she permitted an underage kid to play unsupervised in the front yard of the home on a cul-de-sac. The arrest was made on the false report of a neighbor. The police seized the opportunity to arrest a mother on the basis of "failure to supervise an underage child." The family was traumatized. The mother was put in jail, the child in Child Protective Custody, and the father rushed home from work to see if he could rescue his family from the intrusion of the American Police State. It has happened to many, and Americans sit there sucking their thumbs, hoping the lion will choose another antelope.