Play where? Even if you're happy letting your kid play unsupervised in the park across the street in a high-density area, in the Paris style cities we're talking about the nearest park is still usually blocks away. You gonna send a five year old strolling through the city alone?

Even then, I live in a high-density area with a park across the street and I'd be hesitant to let kids below ten at least go there unsupervised, if I had them. Whereas if I had a backyard I could tell them hey, go nuts, and peek out the window every fifteen minutes.

Of course I'm not defending streets without sidewalks. I'm defending the sort of place I grew up, which combines quarter-acre blocks and trees and parks with having shops and schools and libraries within walking distance.