I would love to cycle almost everywhere, and in the past I've run a large fraction of my errands on bikes. On the majority of roads, though, I do not feel safe doing so, because I have to mix with fast moving cars piloted by drivers that I would barely feel safe driving near, because they're honestly pretty terrible at driving. I know many others who feel the same way - they want to bike more but not feeling safe keeps them from doing it as much as they'd like.

And I can't see how SF could have invested nearly what you claim in biking infrastructure. Their cycling infrastructure is not particularly good compared to most "bike friendly" cities.