I hadn't thought about it but it serves exactly the purpose of a samovar!
An electronic samovar...
For myself, or myself and my wife -- it isn't necessary. I suppose if we drank tea all day it could be. But I've been more of a coffee person.
For a group of people, it is a real blessing to have this.
And let me emphasize, particularly with good Chinese tea, where the whole leaves unfurl in the hot water, you can easily get five or six steepings and the tea remains tasty and interesting -- having water right at hand to refill the little Yixing teapot is especially nice.
Standard tea-bag tea, although good for iced tea, is made of "sweepings" and is basically a dusty powder of tea leaves. As soon as it hits the hot water, it gives up everything it's got. Putting more hot water on that kind of tea is just a cruel demonstration of its inadequacies. One measure of high quality tea is the re-steeping. Probably everyone here knows that...
My favorite Yixing teapot looks a lot like this