My aren't we amazingly judgemental of the kids.
Did you stay within property lines when you were a kid? I highly doubt it.
Since my neighbors and I all knew each other and all our parents knew each other we freely hung out on each others' property.
The only time I spent as a kid on anyone's property whom I didn't know was to retrieve some balls and pucks from time to time from people who were known not to return found objects if you asked them.
In my urban neighborhood there really was no reason to spend time on a stranger's property unless you wanted to steal something - no inviting streams or woods or rock formations or anything like that.
Just poured concrete and tomato patches.