Also because the micro-climate of the penninsula, SF proper, and a decent bit around the bay is almost identical to the rest of the PNW. The culture is also nearly identical.
I went to a bar in SF that had some graffiti all over it. One of the graffiti said "Itching to get out of Portland". I asked inside about it, and they said it's because at the time Portland had a bedbug infestation.
