The straight forward reasons: * Japan is pretty safe. While it's not a good idea to sleep rough, you won't end up dead. * The climate is rather mild. Unless i

The straight forward reasons: * Japan is pretty safe. While it's not a good idea to sleep rough, you won't end up dead. * The climate is rather mild. Unless it's mid-winter or a during a typhoon, the weather won't kill you either. * The culture of drinking after work. * Lower alcohol tolerance, so it's easier to accidentally drink too much. * That the Tokyo metro doesn't run at night, and many people live far from work. Perhaps more interesting: * A lot of people in Japan wear a business suit daily, but make very little money. Most people wear a suite to work unless it requires a uniform. Even then they might go to work in a suit and change. * In general Japanese society is not class-aware. There are big economic differences, but you cannot immediately tell what somebody’s social class is. * There isn't much of an underclass to provide cheap hotels and taxis.