I'm sympathetic with this sentiment but surely it's pretty rare the law actually gets involved? Our kids play outside a lot and no cops have ever raised an eyebrow (except for at our crazy drunk of a neighbor, where eyebrow raising is appropriate).
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.