Believe it or not, carriers would prefer that you not purchase the iPhone. Carriers get larger subsidies for selling other phones, and they make money off licensing software (bloat, screw the customer). In a way, Apple is the ones challenging the carriers. Should the iPhone become dominant on all carriers, the carriers would have to reevaluate their model. They'd either have to lessen their subsidy on other phones (reducing the sale price to customers), or reduce the software licensing (less bloat) to make the phones more attractive, but still get more money per sale than they would on an iPhone.
Like it or not, Google caved to the carriers' demands. Apple hasn't, yet. I prefer Android to Apple, but I also prefer Apple to the carriers. Carriers should be nothing more than a dumb pipe for our use.