This all has 2 psychological effects: when parents feel like they’re just barely keeping this teetering lifestyle from falling over, they become very controlling. Tight control becomes the name of the game: it’s how everything’s done and anyway no one has the time or energy for the unexpected.
Also, when the child represents a gargantuan investment, people become realty protective over their fragile prize. Like a luxury car that you can barely afford: all protective measures will be taken.
Also biologically your whole legacys survival lies on one kid.
Naturally you'd expect this to result in a much higher base level of fear, as compared to when your community was just people you knew and trusted personally.
2. Children used to die all the time from various causes. I remember e.g. the case of Mozart who had just one surviving sibling and 5 who died early. I can't imagine what the parents had to go through - their first 3 children died early. You have to become desensitized to not go crazy.
2. Social status / value of children grew a lot.
Probably 90% of kids in the US live boxed in a relatively small area by roads that are 50ft+ (if not 80ft) wide with 40mph speed limits so that huge vehicles are actually traveling at 50mph driven by people looking at their phone.
In addition, the density of kids is far less. A single street light only have a handful of kids, and probably not all the same age. A neighborhood might have a bunch, but not enough for the kids to mingle.
Plus many send their kids to daycare or afterschool activities. I spend $20k per year per toddler just so they can interact with other toddlers.
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.