Well I suppose that is because we keep on tearing down our history, which is generally even more noticeable and worse because we don't have a lot of it.
The 70's were particularly bad. I felt in the 80's and 90's there was more effort to keep what we still had, but in the current times there seems to be general indifference or disdain for anything not new. I feel that sentiment will change in the next decade or so and there will be a lot of regret - what is quickly torn down can't just be easily undone.
Cities that are attractive and appealing make an effort to keep, reuse and enhance their older buildings.