I think it is just cultural difference. The number of commuters in a lot of Asian countries that use Bicycles are in the millions compared to here in the U.S. I think the concept for this is while you move on the bike, you stop and swing the tablet to the left and tilt your head to look at GPS maps, historical information (for tourists), popular restraunts in the area, etc. Also, countries like Japan and S.Korea are planning to set up solar recharging docks in busy commuting/tourist spots so these tablets can recharge themselves when you move around in the city.
But, cmon, I would rather just carry a backpack with my laptop, tablet, and whatever mobile computing devices I need without it dangling under my crotch as I ride around in Tokyo or something.