I have never been to Japan except as a viewer watching
The Last Samuari! Though I have known many Japanese and have called several friend it would be impossible for me to be able to make any kind of comments about the place of a garden in Japan.

However from what information that I have encountered and what can be found out over the net the basis of any observations have to center around the current realities that modern day Japanese face on a day to day basis. The underlying force in Japan has been Westernization and coupled to it a fierceness in capitalistic ventures. As you know the nature of housing in Japan is simply unimaginable in the USA. Theirs is not a Karate Kid rub on/rub off setting with spaciousness and distinct old style gardens. Such as the exclusive domain of the elites in the nation.
While the gardens you visited are honored they are honored because they are so unique since the availability of space in Japan is so limited and very costly. However, one example of a garden of sorts is the manner in which bonsai growers in Japan keep their plants in a common garden with other bonsai growers (sat on a platform and chained/padlocked to it). Perhaps the only truism would be that the gardens of Japan are the techno displays and the buildings that are the day to day realities of the Japanese peoples.