Would that be because to use it the target needs to be at exactly right height (trickier in tidal water than 'merican lakes) and sitting steady... So not conditions we ever see!
Don't know. I always assumed it was because it didn't work too well.
FWIW, not all North Americans boat on lakes. We may not have the tides you UK guys get (well, not most of us - sorry, Alaskan and Canadian members), but I, for one am fairly well versed in launching and recovering in moving ocean waters. Not saying I always get it right, but still...