1. Housing costs (too expensive)
2. Transportation time / locality (takes too long to get elsewhere in the Bay Area, probably can't live near the job because of #1)
3. Climate - San Fran is rather cold nearly all year round.
4. Because of 1 and 2 likely would not have a garage or space to do projects in.
5. Sometimes things seem rather legally onerous in CA/Bay Area.
6. Regional tunnel vision. When I lived in Northern California I got sick of hearing how it was 'the best place on Earth.'