Actually I was thinking more in terms of aesthetics (and long-term durability) than things like fire safety. Also, the survival rates of older buildings has to

Actually I was thinking more in terms of aesthetics (and long-term durability) than things like fire safety. Also, the survival rates of older buildings has to do with a zillion different factors -- from changes in taste (and ideology) to fate (wars and natural disasters) to the simple economic happenstance of the particular plot of land these structures were located on. That is, the vast majority of buildings are torn down deliberately, to replace them with something bigger or different; to purge a neighborhood of undesirable residents; or to purge collective memory of an unfashionable sense of design, or of place -- rather than because they run into disrepair (or get burned down).