I've been in Japan for the last 7 years and it always bewilders me that so few people own desktop/laptop computers here but everybody is on the internet 24/7. (possibly not only anecdotal...)
I've heard explanations for this involving smaller, more space constrained apartments - and thus less interest in filling it up with yet another machine (tm) and less interest in spending time cramped up at home. This also goes hand in hand with e.g. PC Bangs being more popular over there.
I wonder if this might also go some way towards explaining the salary-man phenomenon. Where employees do excessive overtime at the office. Presumably at the office, they have a work provided laptop/desktop and internet connection. Also the office space may be more spacious in total than their apartments with most of the amenities of home.
Thus they may derive a benefit from staying at the office during the evening rather than going home to a smaller space and no computer.
This is precisely the case for me. I neither have proper space nor the interest to have a computer at home. When I come home from work, spending time on the phone handles everything.