This does bring up another point I don't believe anyone has gotten in to. I don't believe the world ever has been a "safer" or "better" place for kids to be left alone. I know I said earlier that I tend to be rather lenient in personal views of kids being left alone. But while most of us turned out fine, all it takes is one accident or problem, and you have serious issues. This is why guidelines have been set in place as to what age child is likely to be able to care for themselves.
I work in a nursing home, we have a resident who has PTSD after an incident when she was left home alone when she was 10. This was back in the 1930's and she had been so proud that her mother believed she was mature enough to take care of the house for a few hours. That day, a man broke into her house while her mother was out and abused her, and she never fully recovered. In her dementia in her old age, she kept reliving that moment over and over. Now, even if she had been 12 or older, the outcome may not have changed. But it's something to consider with this type of situation. Most of us never had a bad experience being left alone, but there is always the possibility and many problems can be prevented.