There are also still bombs and grenades in the rivers. There are some magnet fishing YouTube channels where you can occasionally see them pulling up stuff like that.
My take (equally guessed): Among the literal rubble spread all over the cities, people constructing everything back up with whatever means possible couldn’t even recognize a mostly buried object as a bomb (instead of just more scrap from a collapsed building).
So less of an active decision to not deal with it, rather one out of necessity and/or not knowing about them, perhaps?
1. https://www.usni.org/magazines/proceedings/1941/december/how...
I might be imagining this but I think that I have seen a report about some systematic effort to trace bomb dropping patterns in aerial images of the aftermath to find gaps in the pattern where something did not go off. But no idea how early or late after the war that happened (if it did happen). And those patterns will only show up for smaller bombs dropped in quantity, not for the big ones.