San Francisco is a fantastic place, but I'm convinced that comments like this one that assume it's so much better than everywhere else that you'd have to be crazy to leave are evidence of a deep (probably not even conscious) need to justify the high cost of living.
If San Francisco didn't cost so much, people wouldn't feel the need to defend it in such ridiculous ways.
What is it that attracts you to SF? I've been there lots of times for conferences and it has always struck me as a so-so place to live, but in my experience there are so many places that are so much better. Cheaper housing, closer to nature, better mountains, better beaches, less fog, better weather, less taxes, fewer californians ;-)
To each their own. I'd rather retire at 35-37 then have to try to stick it out in the tech industry in my 40s and face the ageism that comes with that.
If San Francisco didn't cost so much, people wouldn't feel the need to defend it in such ridiculous ways.