Although anything you can ever want or need can be delivered to your home or found on the internet, it is important to step out of your comfort zone and try new things. Not leaving your home for such a long period of time seems like it could desensitize a person and indicate signs of depression. There definitely seems to be some kind of problem psychologically for young Japanese people.
Many young people in Japan have a severe psychological problem: refusing to leave more for six months or longer. There is no rational reason to stay inside you house for so many months at a time. Furthermore, young people should want to be out and about, instead of being cooped up indoors for so long.
There are some demographic issues in Japan, such as large aging population and lower fertility rates. Young people are not having relationships or wanting to get married and have children. There may be other factors, such as economic and social pressures, but it does not appear to be a healthy environment for young people.
I feel that the fact that this condition has actually been named (hikikomori) is an indication that it is becoming a psychological problem. Many young people but mostly men are inflicted with this and it causes them to remain indoors and isolated for at least six months but for some many years at a time. The fact that these people do want to go out into the world but cannot due to stress ans similar reasons identifies it as a psychological problem.
I cannot sit here and say there is no problem with this especially considering the other problems concerning japan like its birthrate but i have no doubt that this problem is NOT psychological. I actually used to be a hikikomori and i loved it its incredibly fun doing what you want when you want, not being forced to socialize with your average idiot, not having to step out into that hot hot sun. It being a psychological problem couldn't be further than the truth.