Question must be - in a country where population doesn't grow at all and haven't been for a generation+, and housing is not being torn down on a massive scale s

Question must be - in a country where population doesn't grow at all and haven't been for a generation+, and housing is not being torn down on a massive scale so supply of it probably still increases a bit, why is there a need for any new housing at all? Basically, why can't people on average just live in their grandparents' apartments once they die? Housing construction standards have been decent for at least 60 years so these apartments are good and are probably better located than their parents' just because of city growth since.