From reading the ad more closely I suppose that the point was that it was quicker to use the Kem Electric Faucet Heater than to wait a few minutes for your water to heat up in the morning for shaving, or to heat the baby's bottle at night. Who wants to wait a few minutes, after all? This is 1949 (in the ad, I mean) and we are all about the electric mod cons.
Even if (and especially if) they look like the boiler in your basement with a shower head on top. A monolith for your sink! And the name Kem makes it sound like it dispenses chemicals. DuPont may have wanted to give us Better Living Through Chemistry, but this is probably not what they meant.
The Kem was made on East 41st Street in New York City, and hey, that's 5 blocks from where I went to high school in an ancient office building (or rather 2 floors of it) that no longer exists. Not the sort of area you think of when you think of cutting-edge sink technology. I can't remember if we had hot water issues in the ancient office building, but probably.
I keep thinking of things that could go wrong with this thing (electric plug + water = not that safe), but maybe that's just me. After all, it is Fully Guaranteed. Oh, well then! Let's order a dozen.