Monumental protection/urban heritage conservation is alwas costly, full of restricitions and therefore often problematic .... at least @ Europe there seems to be in general a common understanding about cultural assets worth protecting .... btw @ Austria there are also private initiatives to cover the cost (collections for maintaing old churches etc) ....
P.S Modern architecture (aka buildings from 1900 onwards) seem to be a own topic and also here some interesting buildings worth preserving were either demolished or "destroyed by renovation" ....