[QUOTE=Mandylion]
An exchange between two people regarding what is or is not "kirei" is highly dependent on their backgrounds, socialization, and countless other subjective and highly situational judgments. I do not agree that universally something that is clean-kirei will also be beautiful-kirei, nor that they are wholly dependent on one another./quote]

I only partly agree. If it is true that the concept of beauty may have cultural influences, most Japanese would readily agree when seeing cities like Paris, London or Rome that they are much more beautiful than Japanese cities. My wife used to think that some new "mansions" in Tokyo were beautiful, but after coming to Europe, she understood that they are not.

I have discused this problem with a Japanese university professor of architecture, and he agrees that Japan has squandered its historical architecture. Even people like him are only starting to realise the importance of saving historic houses, and try to sensibilise the people. Japan only adopted a law on urban planning this year, he told me.

In my experience, a lot of Japanese art relies on the beauty of imperfections and the flavor/essence of a thing (as in "aji ga aru"), such as tea bowls, buildings, scrolls etc. These things are usually far from physically clean in the visual (and sometimes physical) sense, yet they are still objects worthy of "kirei."
These elements were indeed part of traditional Japanese architecture, but have disappeared in modern concrete constructions.

While Europe rebuilt its old buildings after WWII, I would argue Japan had no real emotional connection to the past and so had no vested interest in restoring old buildings.
Europe could not affor to rebuilt most of its historical buildings (just look at German cities, most houses are new). But Japan was not entirely destroyed during WWII. Many small towns and bigger ones like Kyoto were left intact. The Japanese decide by themselves (and not just after the war, but mainly in the 1960's and 70's) to destroy their old traditional houses, and have done it until now, whereever there was something left to destroy.

In my opinion, for a variety of reasons I will not go into here, the Japanese nuclear family is more focused on the here and now, often cannot afford to restore/maintain old houses with the very high costs of material (to modernize and maintain an old home), energy, taxes, and labor in Japan.
But Japan was in a similar economic and social situation to Germany after WWII. Nuclear families are also something new, and which evolved at the same type as in Europe. Germany and Italy both have lower birthrates than Japan.