This seems like something that only makes sense when water is scarce but electricity is cheap. You’d be constantly losing heat to the poorly insulated pipes.

And you're fully losing heat if you dump lukewarm water down the drain (instead of cycling it back to the heater) to eventually get hot water.

People who do it more or less don't care about the price of energy (except maybe in the abstract).

It's for comfort and convenience.

I have all hot water pipes insulated in my house