I always keep the cheapest Nokia I can as long as I can (they usually last 2-5 years). I have to say I hate complicated phones and like the simplicity of the cheap Nokia (they also usually have a little flashlight function that I prize).
Here we just buy the phone (maybe $30 for a cheap Nokia), and the phone number - another $1.50 or $3, and then just pay for the minutes by buying refill codes at 7-11. I love it, can't believe americans have to commit and all that nonsense.
Some of us do it because its cheaper, some do it to improve our credit score, but the rest of us do it because you touch yourself at night.