Deliberately? Knowing they might suffer?
Of course. My parents let me play out from morning till night, roaming the neighbourhood sometimes with friends, sometimes alone, in a country bursting at the seams with poisonous snakes, spiders, insects, not to mention some locals who would view a white child as a potential meal ticket, or worse, no phone, no rules about when I had to be home, I was totally free during school holidays from the age of about 8. I travelled thousands of miles from home to school and back again alone from the age of 12. My childhood was completely typical of most expats I knew. I was at far greater risk of coming to serious harm from being allowed to roam the neighbourhood or travelling unaccompanied than I would have been left alone aged 3 asleep in my bed and checked on every thirty minutes.
There are millions upon millions of examples of parents deliberately giving their kids free rein, despite the fact that bad things could happen and cause them to suffer. It's only when something goes wrong that the parent questions their judgement and we berate them for their stupidity, but mercifully most times nothing does go wrong. Don't pretend the McCanns are seriously abnormal - they are not.