Also useful when you crest a hill annd there before you is a terrific Panorama, so you pull over to take the shot. In neutral, engine idling but on a slight downhill slope, handbrake on, remain seated, camera out, take shot. And away you go, no trying to fight trying to stop the bike taking off down the hill. A quick stop, click n go.
I know there are other ways but this a great use of the HB.