Uhm, usually because living in the Bay Area is actually a 10x better life for some people. Great weather, very diverse, lots of jobs, public transit is good, arts are amazing, food is amazing, close to sea and ski, etc. etc.
https://www.fortworth.com/about/neighborhoods-districts/cult...
Soon Fort Worth will over take San Fransisco in population, and at the last recession was far less disrupted economically. Speaking purely from data and statistics Fort Worth is more diverse than San Fransisco with regards to ethnicity, religion, nationality, and so forth. And I doubt there is a substantial difference in the diversity of food options since I have been to San Fransisco. The weather and public transit are likely superior though.
Otherwise, if I were single and had 10x the income I would likely agree that the bay area is a more fun place to be.