Those hills severely limit visibility on so many of those crosswalks, and if you’re driving up one of them, and the sun is in your eyes, I don’t know how you would approach an intersection safely.
If you can't see where you're going then your speed should be as low as possible. I'm not from SF so maybe it already exists, but ideally there would be traffic calming measures such as lane narrowing, speed bumps, etc and so going faster than around 20 mph or so would feel very unnatural.
Well Gaetz was blocked so it does seem they do have some sort of limit (even if that limit is deep underground).