And when they start to have to use public transit to get to secondary school with 10 every day, it makes sense that they start by going shopping or similar places with 8/9 by bus/metro/etc.
I was driven to school, though I walked 250m to a neighbours house half the time for the lift. Walking to school would have taken over half an hour at a good, adult pace.
(The fear was probably traffic more than strangers.)
From 10 on I had to go to a secondary school which was 4.5km away, so I usually used the bike, but walked sometimes. At that age I also started using the bus to get to the other side of the city, or to take the bike and go to a cinema 12km away with friends, etc.
We obviously had almost no traffic here – except for busses and bikes. And construction vehicles.