The street I spent my childhood on there was about 30 kids under 10 years old. Now there is about three. My family moved away but I recently checked and the girl next doors parents have lived there ever since. They're in their 80's.

Mulling it over I think uniform single use zoning/construction is 'bad'. I saw presentation by a guys showing various housing. One of them was a very nice 1920's era apartment building in Redwood city. One of his points was it'd be totally illegal to build something like that today.