Aside from all the good points made by others, it’s interesting that kids are not innately prepared to face many hazards in the modern world alone.
Children can find out that rocks hurt through trial and error throwing pebbles at their friends, and they will figure it out. They are instinctively wary of things like snakes.
But the threat posed by electrical sockets, stovetops, cars, bleach, power tools, and so forth are not forgiving to experimentation and not instinctive.
See even that doesn't exactly explain the trend. My parents generation had all those risks and more (more deadly power tools and electrics) and the parenting was still absentee at that point. Sure they got into trouble with these things on occasion but a kid learns pretty quick a stove is hot and not to walk into a busy road. In japan they send young kids on errands directly into the modern world where they have all the same risks as they do here, because they understand the value of giving kids a bit of credit.
Children can find out that rocks hurt through trial and error throwing pebbles at their friends, and they will figure it out. They are instinctively wary of things like snakes.
But the threat posed by electrical sockets, stovetops, cars, bleach, power tools, and so forth are not forgiving to experimentation and not instinctive.