It's because of the geography. Southern California and Arizona especially were impossible to live in until after Air Conditioning became cheap and widespread in the 1950s. At that time, modernism in architecture and city planning was at its peak: build it big, build it simple, and build it for cars.
This thread is filled with strange ideas. I live in San Diego. I know people who don’t have air conditioning, and they’re fine. The weather is mild unless you get 15-20 miles off the coast, and then it’s still not that bad 90% of the time.
Southern California? There are tons of places in LA and San Diego where AC is entirely optional and often not installed. 72 and sunny is a stereotype for a reason...
Desalinization is expensive compared to pumping water out of the ground, but it's dirt cheap compared to ubiquitous air conditioning and/or depopulating cities.
The coming droughts will affect agriculture, but not the cities.
