The problem is. the number of people, and the number of devices, especially oldera analog
A lot of people still use crappy old analog phones, so until theyve all gone we suffer.
4G is coming, which is a lot better, much higher transfer speeds.
The states is often behind on technology like this, the people are real luddites and/or slow to take on new technology, a deeply paranoid consumer base
So far sprints been working the best for me for calls, AT&T non GSM networks works well too, their GSM sucks beyond belief.
T-Mobile is ok, but they are rinky dink.