It's probably the result of the lobbying power of a conglomerate of automotive stakeholders, formed in the 20s/30s. [1]
[1]http://en.wikipedia.org/wiki/Automotive_city#The_road_lobby_...
Reality is also that humans generally prefer having some room and space. Crowding people together CAUSES problems. If you've ever lived in an apartment building, you know this.
But it can't be any of that new technology enabling higher standards of living. No, it must have been an evil conspiracy. We should all ride bikes and live stacked on top of each other.
Data to support this? Every study I've seen recently shows that people are moving INTO cities, not out of them.
People are leaving the dense NE cities and going to the less dense south and west ones.
To pick the largest city in the US, the population density of Manhattan went from 21 in 1910 to 12 today. And Lower East Side went from 70 to 16.[1]
Also look at construction statistics, new home construction outpaces population growth, people are moving into less dense areas and need new housing.
They build a bit less than 1 million homes every year, and most of those are single family homes.[2] Population growth is about 2.8 million each year, but that's people not families.
[1] http://www.nytimes.com/interactive/2012/03/01/realestate/man...
[2]http://www.economicpopulist.org/content/new-residential-cons...
I'll also present you with this about apartment construction now driving the economic recovery, not single family homes (disclosure: I work for rentals site hotpads.com, owned by Zillow) - http://time.com/102822/housing-apartments/
WRT NY's density falling, it could be an outlier or the norm. Still, from what I understand overall population densities are increaing in the US. [1]
[1] http://www.nytimes.com/2014/04/17/nyregion/suburbs-try-to-ho...
edit: Clarification and spelling.
Some cities are like that, and others aren't. People can vote with their feet. Guess which one people like better? (Hint: People have been moving out of dense cities for 100 years now.)
Are you planning on forcing people to accommodate themselves to your definition of the perfect city?
> We have disparate clusters/districts related to activities like 'work', 'play', 'shop', and 'sleep', rather than having these constructs evenly interspersed.
Is that supposed to be a bad thing? The world is not sim-city. Not everyone wants to live near a shopping area.
> We have supermarkets instead of markets.
Markets are not large enough to carry everything, so when I lived in a place like that I never went to the market, so I got the worst of both worlds: High density (i.e. traffic) plus a long drive.
I moved out.
You are acting as if the layout of cities was a commandment given from on high, but actually cities are laid out as they are because people like it that way.