And yet, the argument could be made that preservation of those sites may keep us from straying as far as we otherwise might. Preserving our history keeps us in touch with it.
I've heard Mark Levin, for example, frequently recount the inspiration and sense of awe and reverence he felt as a child in Eastern PA visiting Independence Hall. Would he be the same conservative voice had he not experienced that in his youth? I don't know, but I'm guessing it wouldn't be quite the same.
Then have the government own them (instead of taking massive swaths of land out west); I understand their significance, but that in and of itself should stop private owners from obtaining them.
As urban areas fall apart, local groups try to prevent the demolition and sale of old sites because it will expose the cultural vacuum/decay; if the owners never took a penny, and it has only local importance to a select group, let them buy it or shut up. This is a real issue in an area settled by the Dutch 300+ years ago (northeastern NJ).