What would have happened in the old days?
Honestly? I'm not saying it's a good thing, but someone (ok, normally the mother) was always home.
In my street I knew of one child, apart from me, whose mother was out at work. My grandfather was her unofficial guardian outwith school hours, so when we played outside, he was responsible for her as well as my brother and me. Grandparents often lived with families so the children I knew were probably more "parented" than children now - that's probably why we liked to play outside.
1950s children may seem to modern eyes to have had huge freedom, and to an extent we did. But communities were different, people knew each other, neighbours kept an eye out for "strangers" and children were generally bossed around by any passing adult. My friend and I used to wander a fair bit at the age of 10, but chances were we'd bump into someone who would ask if our mothers knew we were so far from home, or in fact suggest we went home that minute.
I know people don't like that sort of thing now - you get the downside that people know your business - but on the other hand, it made the world a lot more secure for children. We did our roaming feeling unsupervised, but the reality was that we were never far from a responsible adult.