Cost is too high
Yeah, they signed up for shared data as the unshared prices are through the roof! They simply can't afford to spend that much on data charges. Shared at least gives them the feeling that they can get data for everyone but then they need to really work hard on not going over. I would venture to say that many will go over and end up paying as much under a non-shared plan. It's really a way for carriers to get people in the door and lock them into a 2 year contract.
I'm wondering when consumers will start standing up for themselves by not allowing themselves to be gouged. iPhones end up costing customers a lot more then the plan fees and shared data is no big savings either. It's actually a step back. There are now two carriers that offer _true_ unlimited data when AT&T and Verizon are going the opposite direction.