At some intersections the sensor loops literally never activate for bikes (especially carbon bikes with very little metal). If you don't run the red light then you'll be stuck there until a car happens to come along and trip the sensor for you.

Okay, that seems ultra relevant to the ~100% of bikes that routinely run red lights in San Francisco at fully trafficked intersections where the sensors are clearly already tripped.

So you dismount and cross as a pedestrian. I mostly cycle, and the lack of bike sensors at some intersections is occasionally annoying but not a reason to break the road rules.