The reason is being, apple itune in the internet needs a credit
card to enter, apple iphone comes with no games, no songs, but all
is in itune, it is not you need to pay, but in itunes you can both
free and pay stuffs, without a credit card, you cannot surf itune
ya. So, those telcos selling Iphone will insist that you have
credit cards register first with them so that you can go into itune
to surf.
If you are buying a iphone over the counter without any
contract, you can use cash if you dun have a credit card. But later
when you want to surf itune, you will have problem, and your Iphone
will be not be able to enjoy what apple truly offer you at a
discount rate for any downloading.