Giving examples of the behaviour of other careless parents doesn't somehow excuse the behaviour of the McCanns. It just shows that there's other careless parents out there.
I loved reading, but with three children under 5 I didn't pick up a book for years. Small children are a full-time job. If there's a pool nearby you watch them all the time. If you're in a crowded place you hold onto them.
You could read when the children were tucked up in bed, presumably safe & sound from the risk of an abductor entering the premises. Of course, there is always a risk that a 4 year old will come downstairs, leaving the safety gate open at the top of the stairs....and it's too late when the 2 year old trips down, head first. So I guess you sit at the top of the stairs all night - right?
You keep the pills, sharp objects, electrical goods, matches, out of reach.
You just don't expect someone to illegally access your home & steal your child.