It really isnt that hard to understand. People aspire to what they know. San Diego is a place of transplants most of whom grew up in very nice but less expensive housing markets. They come here for good well paying jobs with the expectation/hope that they can live in a nice cushy suburban neighborhood like the ones they left behind. They dont aspire to 50 year old fixers in so called prime locations.
The other issue is that when one moves into older, established neighborhoods they are more likely to encounter older neighbors not interested in socializing with newcomers rather than their peers. Moving to a new neighborhood means everyone is in the same boat and anxious to meet each other. Communities come together very quickly under these conditions.
