In reply to Denni:
I've discussed this a lot with friends in the context of us looking after our godchildren.
Essentially it comes down to "What we were allowed as kids, and what was normal then, and did us zero harm, is no longer socially acceptable, regardless of the actual risk to the kids, which is as near zero as makes no odds".
The attitude of parents varies from our friends, who mostly find it incredibly frustrating that they cannot give their children the freedom they need to grow and that they would like to have(1), to some sections of society (notably one of our neighbours) who follow their children around the back garden at a distance of six feet in case they injure themselves.
Personally I think the helicopter parents should back off, but that's never going to happen with the law the way it is and society the way it is now.
(1) e.g. From age 11 I got the train to school on my own. Our friends feel they cannot let their 13-year-old daughter get the train from Gloucester to Birmingham on her own to stay for a weekend with us, not because of the risk to her (all agreed as zero), but because of the significantly non-zero possibility that some interfering goit will ask her "so, where are your parents?" and report them to social services and the kid to the police.