1. Cultural diversity. I'm an immigrant and having lived in Seattle, Boston, NYC, and Philadelphia, I'd say the Bay Area is hands-down the most welcoming of all of those. It may seem like a small point but my parents and family can walk downtown in traditional clothing and no one even notices. Not true elsewhere.
2. The weather. Initially I thought this was overstated but I've realized after two decades in Boston and Toronto that seeing trees without leaves for six months of the year has an impact of my mental health. Seeing greenery, and enjoying warmth, even in January has a huge positive impact on my health.
3. The optimism. Most people I meet in the Bay Area are optimistic about how a problem can be improved. That's rare and I haven't found that in other cities or countries I've lived in. As an entrepreneur that's a wonderful to be part of.
Detractors of the Bay Area seem to hang out in very specific circles of friends which seem to be rather homogenous. A solution for me was having kids who go to public schools. I end up hanging out with people who are typically not other tech founders.