In fact, we brought up our children when we did not have a car. We took them to school on our bikes, and from the age of about five they would ride their own bikes to school, and from about ten (?) I think unsupervised. We did long loaded cycle touring holidays with them, including in the Alps, when my then ten year old daughter would descent the pretty long Maloja Pas in the Alps on her own bike.
That's feasible for some people even here were I live when the weather is good, and they live close enough to their children's school. My sons school is about 6 miles from my home, and when you consider the extreme heat and extreme cold we we get indifferent parts of the year its just not realistic.
In the late summer when school starts we can have days where the humidity pushes the feel like temp well north of 100F. we get the other extreme in the winter time as well, last year we had a 2 day period where the wind chill was between -30F & -40F. Most schools actually closed on safety grounds.