I agree with all those who have admitted to sometimes leaving children unattended whilst on holiday. When my first born was a baby we sometimes stayed in hotels with a baby monitor, whilst we went down to the dining room in the hotel. Once he'd fallen asleep, he was out like a light, I remember thinking we were lucky when other parents halfway through their meal were contacted by reception to say their baby was awake. Anyway all that ended with number 2, who wasn't so obliging.
Talking of number 2, when he was around 7 or 8, we were staying at a hotel in Spain spending an afternoon around the swimming pool. Took my eyes off him briefly, he'd disappeared, that disappearance was for several hours, I can't ever remember being so frantic and out of my mind with worry. The hotel was putting out announcements on a tannoy, eventually staff went knocking on all the room doors and there he was, wandered off with another little boy who wanted to show him his Action Man toys, both had been whiling away the time in his room with an array of superheros oblivious to the fact that a full scale search was going on. That was long before Madeleine disappeared. I think a lot of us looked back with a "there for the Grace of God" I'm sure it changed parents' behaviour in the aftermath. I have nothing but sympathy for the McCanns, The Bulgers and the parents of the little blonde boy who disappeared in Greece many years ago. Hindsight is a wonderful thing, sometimes it only takes the blink of an eye.
I would suggest many of us cast our mind back to our own childhoods, our parents generation were positively laissez faire as far as the hands off approach in being allowed to roam around far and wide , mine certainly let us wander off for hours on end at an early age. I don't remember parents being castigated quite in the same way, helicopter parenting just wasn't a thing if my memory serves me well.