So can I have the right to broadcast my own GSM signal in the 900 MHz range, or a perpetual sweet-heart franchise agreement with my local municipal government to run last-mile internet to my neighborhood's houses?
These are natural monopolies we're dealing with. My options are constrained to carriers that have been granted guaranteed access to public airwaves by the FCC. The carriers then use technical (carrier locks), legal (contracts), and social (difficult cancellation processes) means to lock consumers in.
The carriers then collude with handset makers to restrict consumer choice further by locking handset features, and restricting the applications that they run. There are ways around this (such as buying third party unlocked, unrestricted phones), but carriers and handset makers leverage their government-backed market position to discourage consumer adoption.