In old times, to boil water was an arduous time-consuming task, considering that one had to start a fire in a stove (using either firewood or charcoal).
Thus, almost every household had one or more Thermos Flasks, to keep the boiled water hot and handy for dispensing at any time. I remember we had two big ones which were used to hold plain hot water, and a smaller one to hold hot coffee. But the coffee always had a sourish taste after a while — I disliked that.
Oh by the way, every now and then, one of us would manage to drop a flask on the floor and shatter the glass inside, because some lizard would emerge unexpectedly from behind the flask while it was being carried, and cause panic. Cicakphobia, I suppose.