Less air pollution does increase productivity (air pollution is actually really bad for your mental performance, it's a surprisingly strong effect) and it seems to me "the ruling class" does consider it seeing as the Clean Air Act exists.

Btw, Japan has walkable cities of course but also has low inequality (but not so high wealth). Approximately nothing is known to increase birth rates except for being highly religious though; it seems they mostly collapse when people have anything else to do for fun besides have sex. So basically it's caused by being on your phone too much.