While it's true nobody moves out of a 10 acre farmhouse in San Bernadino because Long Beach is too crowded, the low density parts of the state don't have any jobs and aren't particularly nice places to live to start with. So density in the nice, employment rich places matters.
San Francisco is an outlier. It attracts people who want to live in a dense urban environment and has a reasonable public transportation system. In most places higher density directly translates into less free time as a result of longer commutes.
High density doesn't directly translate into longer commutes. It directly translates into better jobs. Since people are willing to travel longer distances for better jobs, longer commutes are an indirect result.
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While it's true nobody moves out of a 10 acre farmhouse in San Bernadino because Long Beach is too crowded, the low density parts of the state don't have any jobs and aren't particularly nice places to live to start with. So density in the nice, employment rich places matters.
San Francisco is an outlier. It attracts people who want to live in a dense urban environment and has a reasonable public transportation system. In most places higher density directly translates into less free time as a result of longer commutes.
High density doesn't directly translate into longer commutes. It directly translates into better jobs. Since people are willing to travel longer distances for better jobs, longer commutes are an indirect result.
In the long run that's true, but if you're already living somewhere and the density increases you're going to have a longer commute, most likely.