I can't find the article that originally referenced this... but the idea that Apple would buy a phone company was made obsolete with the AT&T service issues that were present in the United States. By commercially separating the Network from the Phone - a new concept for the carrier-lock in situation in the states - it removed a large segment of risk from the user experience. How many times have you heard "the iPhone is great, but AT&T has terrible service" or something else along those lines? It's a common argument.

People don't understand the difficulties of having lots of data on a large-scale network across thousands of miles of cities, countrysides, and elevation differences. They do understand if a computer or phone is slow, though. This way, there are problems, but it's not because of Apple and their immaculate product. Why tarnish your brand with something people won't understand?