The reason that Japanese people access the internet on their phones more than from computers is that they spend a huge amount of time on trains where there is nothing else to do. 1-2 hour train commutes each way are commonplace. They are not supposed to be looking around at other people on the train and they aren't supposed to talk on the phone. Most of the time you will be standing up because there are no seats available. What else are you going to do if you spend 2-4 hours a day standing still in one spot trying not to look at anyone?
What else are you going to do if you spend 2-4 hours a day standing still in one spot trying not to look at anyone?
Read a book? And indeed, there is about an even split between people reading books and people playing with their mobiles. Remember that a lot of the trains run underground, and not every line has a cell phone signal for every provider.
I think the reason for the popularity of the mobile Internet is that there is no complexity involved to use the Internet from your phone. Everything is designed for the phone; you can buy things, you get billed for it, and it shows up at your house. On the computer, you have to type in details every time, and credit cards aren't very common, so you have to arrange some other way of paying. It's a pain.
Some other nice integration -- if you buy a JAL ticket and check-in with your mobile, you can use the phone as your boarding pass. I can check in for my flights on my US-based cell phone, but that's not going to get me through security. (Note that Japan also has realistic airport security, unlike the US.)
