It’s a thing in the US too, but not common. I always understood them to be expensive to use, as you always have a pump running and hot water cooling down and needing reheating.
Yes, in the Soviet Union, hot water was a byproduct of production of electricity - using combined heat and power, it was a waste heat. And it used lots of electricity to make weapons to advance dictatorship of proletariat, so there was plenty of free heat, too.
My house originally had a recirculating pump for the hot water but it burned out. Somehow though, it still (mostly) worked and had instant _warm_ water.
I think it was through natural convection/circulation - the hot water expanded in the tank and pushed it through the recirculating loop?
So maybe there's a good-enough solution that doesn't require a pump, just a return loop.
Now I have an on-demand water heater with a built-in recirculating pump, so it's instantly hot :)
Hot water recirculating pump. https://www.familyhandyman.com/article/hot-water-recirculati...