Probably because we don't have Early Termination options here - once you're signed up you pay for the term of the contract, or pay the rest of the contract up front to get out early...
I had an iPhone then an iPhone 3G, but I now use a Nokia E71.
The 3G iPhone simply didn't have enough battery to get me through an average day and if I used it as an iPod too, then it would barely get me through the morning.
I got the phone replaced for an unrelated issue (cracking case) and it was still no different so now my Daughter has an iPhone 3G (which she is pretty delighted about), and I have a phone that does what I need it to do much better then the iPhone and a 32GB iPod touch for my media and other Apple goodness.
Personally, I find the combination suits me far better than having everything on a single device...