The city that I live in faces similar issues, even though it is young by international standards, and those issues exhibit themselves in very peculiar ways.
If we were talking about a building that is actively maintained and played a significant role in events, I can understand the desire to preserve it. Yet, more often than not, the buildings are decayed due to neglect and very few people actually care about the building until it is about to be torn down. Worse yet, the structure has frequently been altered to the point where it is no longer of architectural interest. So yes, this is a concern from the perspective of the greater needs of cities. Which is why I was puzzled by the opposition due to the environmental impact.
On the other hand, I suspect that these attitudes stem from something other than a desire for preservation. It may sound noble to talk about the greater needs of cities, yet some mighty nasty projects have been undertaken in the name of redevelopment. For some people this brings up extreme cases of forced removal, serving the needs of special interests, or simply creating inhumane environments.