Or, you know, people like to live in houses with a yard, where there might be wild animals living around or a forest somewhere within an hour's drive, and prefer that over cramped hovels.
Whereas if our cities were denser, there'd be more open space left, that is easier to access, by potentially more people. Density != cramped hovel. And density doesn't mean everyone lives in a highrise. There's points between single family homes on quarter acres and 60 story skyscrapers.
Edit: I highly encourage you to checkout some examples of cities that saw most of their growth pre-auto:
Here's my personal favorite - Leipzig Germany, metro population around 1 million: https://www.google.com/maps/place/Leipzig,+Germany/
A wide range of uses, densities, housing prices and modes of transportation (dedicated bike infrastructure, transit, and yes even cars). But the compact development area can leave so much more room for green space, nature preserves, public parks, agriculture, watershed protection. There's even many buildings that have yards - it's just everyone doesn't get their own acre.
https://en.wikipedia.org/wiki/Bombing_of_Leipzig_in_World_Wa...
Here is a video comparing a tram ride through Leipzig in 1992 with one in 1931:
The Nazis had the same attitude before. Cities had to be car-centric, that's why they moved on with the Autobahn and created Volkswagen. The obligation to use bike lanes (Radwegebenutzungspflicht) was issued under the Nazi regime. It was part of the fascist mindset that cities are made of concrete (instead of children playing in parks).
[1] http://www.ardmediathek.de/tv/Reportage-Dokumentation/Unsere...
As far as density, people per square kilometer.
10,831 NYC
5,344 Boston
4,447 Chicago
3,198 LA
1,985 Detroit
1,900 Leipzig
1,414 Houston
Ie Leipzigs boundary for that number includes the city and undeveloped/agricultural/rural areas in the surrounding metro, where Detroit's number is the developed city limits, excluding the suburbs, exurbs and agricultural places in the metro.
I don't mean to get too bogged down in this point too much. I wanted to point out there are plenty of lessons we can learn from pre-auto cities to make our future more livable.
No, Leipzig's boundary for that number does not include their larger Urban Area. Looking at the metropolitan area population of those cities Leipzig is 843,619 while Detroit, the rust belt city you mention, is over 4 million according to OECD.
If you compare the official city limits with the satellite view you will see the developed area containing most of the population is much smaller than the city limits, and you might understand what I am getting at. I think the appropriate measure here would be the weighted density, closer to representing the average density a person there would be surrounded by.