The cellular market for voice calls is fairly well saturated. The UK, with 60 million people, had approximately 70 million active cell phones a couple of years ago.
The cellular companies are trying to use their expensive networks for other things. For example, the iPad 3G is selling quite well and can't make a voice call. I designed vehicle tracking devices that had no connection to the audio circuits as it could only use texts and GPRS data.
All those data uses need more bandwidth for faster download times, to either give faster browsing, or to allow more users on each cell.