It depends on what you mean by "unsupervised". The people that lived across the street from us in our first house would shove their kids outside from morning to night. They depended on the neighbors to care for them, even feed them. One day, while pregnant with her seventh, the mother stopped me to ask if I had seen their 10 year old. He had left the house at 10 in the morning and she had no idea where he was, and it was now 6 at night. One night, we found their three year old in our backyard kiddie pool after dark. She was blue and shivering with cold. My husband wrapped her in a towel and took her home. He advised her father to get her out of her wet bathing suit and get her in a hot bath. Not five minutes later, she was outside riding a Big Wheel in the middle of the street, still in her wet bathing suit.

The kids weren't "abused", but they were certainly neglected. It was disgusting. Would these people be arrested for their kids playing unsupervised? Yes, but they would have deserved it.