Japan only really started doing that as their population began to fall. It's a situation lots of Central Europe is starting to experience too. Before then, the land the Tokyo Imperial Palace occupised was worth more than (theoretically, at prevailing market rates) than all of California.
I'm not sure I buy that simplistic argument. As a counter-example, residential property in most exUSSR experienced significant price increase during previous 30+ years while populations of those countries mostly decreased during that time (and often much more significantly than in Japan). Why? Because people were (and often still are) convinced that it is best investment for them long-term.
