These days have little to do with historically. The bay is hemmed in by hills and water. LA is similarly hemmed in, creating a nice bowl that traps pollution. Seattle and Portland are both hilly, you are not at a flat grade. Berlin, Amsterdam, Copenhagen are all flat in contrast.

Cities with lots of hills in Europe don’t have as many bikers or biking infrastructure. Eg Lausanne unless you want to go for a jaunt by the lake. Cannes was the similar during a short visit I made 20 years ago. Hilly south Europe (Athens, Rome) doesn’t seem to like bikes very much either.