Preserving architectural works of extraordinary aesthetic merit is every bit as worth expending social resources on as preserving paintings, beautiful waterfalls, adorable pandas, and other things we enjoy enjoying. And then there's San Francisco: "Proposed landmark areas, some already under Planning Department consideration, include car dealerships along Van Ness Avenue, described by preservationists as 'automobile support structures.'"
The problem here, roughly speaking, is that if you want to acquire some land and build a museum and stock it with paintings and hire staff and open it to guests and mount exhibitions that you end up with a pretty clear bill. The monetary costs are reasonably clear, and while that by no means ensures consensus it does at least create a framework for deliberation. But the cost to a high-wage high-rent city of preventing the redevelopment of car dealerships is both extremely large and largely hidden from view. The City Council isn't going to be asked to formally appropriate millions of dollars to preserve these automobile support structures. But the costs are real just the same.