So here's a theory. Not really related to bicycles, but to the extending leashes, because they are a menace to everyone including the dog. These are "normally open" devices. The leash spools out unless the walker takes action to press the button and activate the ratchet. It should be "normally closed" where if the walker does not hold the button, it does not spool out. It would require his attention.

Similar theory for strollers - they need a deadman switch, that brakes if they are not held onto.