This idea comes for free if you're also using hot water in radiators as a way to heat your home at the same time. Which the Soviets did. And in the Soviet era, they also were generally heating that water at the district level, then circulating it to all of the homes. This can only be workable if you're pumping the water continuously. So the cost of the pumping is just part of the overall system.

Places where this was built up, still generally use it today.

In the USA, nobody ever built the district wide heaters. Nor would they be viable in the suburbs that many of us live in. We generally use central air instead of radiators to heat our houses. And the result is that constantly circulating hot water is significantly more expensive for us.

Does that answer your question?