At the risk of bringing the tone down, there are two big changes from the days of yore when kids would do this sort of thing.
The first is the whole “stranger danger” thing; parents are a lot less willing to leave their kids outside unsupervised talking to a parade of strangers pulling up in their cars than previous generations were. Which is understandable, I suppose.
The second, alas, is simply that younger couples - with kids of the age that do this sort of thing - are much less able to afford homes in the sort of neighborhoods you can do this thing in. My parents have noted that the number of kids in their nice middle-class suburban neighborhood has fallen dramatically since the days when we were kids, and the houses are all owned either by older couples who bought them when they were more affordable (like my parents) or by professional couples who moved in when their kids were mid-to-late teens at the youngest because it took them that long to save up for them.