There's plenty of people who live in SOMA, Bayview, Dogpatch or the mission commuting to SOMA and FiDi who barely have hills at all. I used a single speed bike

There's plenty of people who live in SOMA, Bayview, Dogpatch or the mission commuting to SOMA and FiDi who barely have hills at all. I used a single speed bike for years when I lived in SF. I'm not saying they're a great fit for everyone -- but there's definitely a market.