You can’t safely dock, single-handed, if the engine shuts off when you step away from the helm.
Agreed. The primary function of the kill switch lanyard is to disable the engine every time you reach for your drink or turn to look over your shoulder.
I have mine on my boat key set with a good long coiled lanyard. I wear it when boating alone, when in real bad power boat traffic (which is not all that uncommon on the Lake of the Ozarks) but I frequently have it disconnected from my vest when doing things that will cause me to leave my seat.
Likewise, I wear an automatic inflatable vest. I know of too many old guys hitting their head or something else causing them to hit the water.