It’s Foucault’s interpretation of the panopticon. If we know that we may be watched — and punished — we self-police into following the norm, even if we do not know when we are being watched or that someone is necessarily monitoring us individually.

When I was a kid in the 80s none of this was an issue and I was free to roam. Starting in the 90s this became an issue and not only will parents not let their kids roam but the kids themselves have less interest because the norm is to stay in or only go out when supervised. You know you are doing something slightly wrong. It only takes occasional reminders like this to reinforce the rule, once established.