BART and Muni beat most other transit systems in the US, but pale in comparison even to London, let alone Berlin or Frankfurt. If you're heading anywhere west of downtown SF, expect long waits for connecting buses...which often simply fail to appear, NextBus's predictions notwithstanding. As an earlier commenter mentioned, it's not uncommon for SF commuters to finish the last leg of their commute with a cab.

And a lot of people in NYC don't have cars simply because they can't afford to park them, not because available mass transit makes them unnecessary.