My experience of travel suggests to me that honking is cultural: what's normal for Mumbai doesn't happen in London.

In the UK, the horn might be used to "wake up" a driver in front - e.g. the traffic light has gone green, the driver in front isn't paying attention, so the car behind might sound a short honk to alert the driver in front that the light has changed. There's also the annoyed "you cut in front of me" / "you did something dangerous" long blaring honk.

Those are the two main accepted uses of the horn in the UK, so there isn't much honking in UK traffic jams.

The ones in SF’s FiDi are, but the highway ones seem quiet. Beats me why.