Maybe a lot of people were on their cellphones while banking, getting distracted and forgetting their money/card at the machine. There's no way they would use any sort of wireless standard for money transfer, it should all be wired connections.
Edit: I found the reason: A Tokyo area bank has begun installing devices that jam cell phone signals in order to prevent elderly citizens from becoming victims of phone fraud. Swindlers have been targeting seniors, telling them to go to the bank and all the while stay on the line while withdrawing money at cash dispensers. Now a Chiba prefecture bank is the first to use mobile-phone signal blockers near its ATMs. www.ubergizmo.com/15/archives/2008/12/tokyo_installs_cell_phone_jammers_at_atms.html