In part I think it's also the development of greater paranoia and zero risk tolerance (for whatever reason). It seems like nowadays if you let your kid play by themselves, or even if you aren't hovering over them close enough, some other parent will call the cops and you'll get in trouble for being a "negligent parent". When I was a kid (80s/90s), I'd ride my bike around the neighborhood alone or with friends, walk to friends' houses by myself, etc., and that was the norm.