I am a big desktop user, but i do not live in Japan, i only travel in and out of Japan for work and i always use a laptop very small and light. but i do have 4 laptops different size and weights. small one for travel only.
When i was shopping in Japan with a friend who lives there, i was looking at PC's, I ask my friend why not buy a desktop and they said because of the size of their apartment and because moving from one apartment to another not easy. So they person a laptop because of that and laptop is portable for their work/personal use.