This becomes especially clear when you realise that Los Angeles's watershed extends 1,500 miles eastward (about 2,400 km), to the Colorado River and the eastern front of the Rocky Mountains. Los Angeles has (under western-US water law) senior rights to water, over those of users far upstream of it.
Water supplies, and the rights to them, are based in large part on the economic (and hence legal and legislative/political power) of metropolitan areas. Since a large city with large rights effectively sucks dry land from 100s or 1,000s of miles away, population concentrates into a few centres, rather than being distributed across the land.
This contrast shows up most especially in the "Earthlights" images of the US mainland at night, where east of the Mississippi river settlements are dotted evenly through the landscape, but thin rapidly as one heads further west, dissolving into a few mega-concentrations: the Colorado front, Salt Lake - Provo, Albequerque, Phoenix, Las Vegas, LA-San Dieto, the Bay Area, Portland, Seattle. A few more-populated regions exist (the Sacramento-San Joaquine valley, the Willammette valley), but these are sparse compared with the Eastern US.
https://upload.wikimedia.org/wikipedia/en/4/48/Earthlights_d...
For the most obvious - Once you're off a municipal water supply (which of course, has to have an adequate source of water in the region), available water resources/aquifers are often very limited and minimum lot sizes have to be large because the land can't support higher density housing.
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If you build anything even approaching "normal" suburban SFH housing, you're just going to have all the wells you'll have to sink run dry in a few months and the properties will be uninhabitable. Seeing a 2 acre minimum lot size isn't necessarily a "keep the poor people out" thing.
To be clear, I am mostly not referring to the cities mentioned in this article, but housing development in smaller mountain towns and the rural/semi-rural areas up in the mountains.