It's also one of the more lucrative. Prices are getting less and less, flat rate plans are the norm, coverage is going nationwide, and features are changing every few months. And customers are biting. I am sure price is the major factor. But, with prices so low and so similar between carriers, other factors, such as coverage and features, become more important.
Price Let's start with price.
I could have started with vendor, but most people are currently shopping on price. This is fine if you want the phone for emergencies - which is how they are marketed. But, most people are accustomed to cell phones and want to use them. And, the only reason to keep using an analog phone is when you are not in a digital coverage area. Minutes range from 20-350 and plans go from local to regional.