Well they can be, until they boil dry, and the thermal cut out kicks in. Prior to the late 70s / early 80s so called "automatic kettles" were not necessarily a

Well they can be, until they boil dry, and the thermal cut out kicks in. Prior to the late 70s / early 80s so called "automatic kettles" were not necessarily all that common in the UK, and one had to manually switch them off. I certainly recall a time or two with a kitchen full of steam due to forgetting about putting the kettle on.