Part of the answer also lies in the real-estate market. Anything in Japan that involves buying land for the purpose of new development is both expensive and time consuming. Better elderly housing would benefit from revision of taxes dealing with real estate, zoning statutes and other related regulations. Right now one of Japan's greatest concerns is the lack of new industries to push the economy back toward healthy growth. Information technology has attracted a lot of media attention, but that industry is too small to be much of an engine of growth all by itself.
Society needs other engines as well.
Housing for the elderly could easily play this role. The need and opportunity are obvious. The economy would benefit, and so too would the lives of older people. Just get the government out of the way and let the market work its magic.