Sure, it would be convenient for the Russian soldiers to hole up in a building with Ukrainian utilities supplying it with heat and light and water. But they are far less reliant on it than the Ukrainian civilians where loss of power could create a huge humanitarian crisis that the Ukraining govt has to deal with and distracts them from the war effort.
In short, it’s a minor inconvenience for the Russian troops as opposed to a huge problem for Ukraine. So the tactic is a good return on investment….at least on the surface.
The problem with that is that the Russians have had supply problems and alot of their soldiers lacked basic gear when the war started…and as conscripted soldiers show up also with a shortage of gear, the Russians are likely going to be in for a hard winter.