Why do people buy sim cards

[bsrftk]

I was looking on E-bay and noticed taht a lot of people sell SIM Cards.

What's the deal with that?

I mean I didnt even know we can buy SIM cards from carriers standalone from the phones unless it's prepaid?

Isn't it pretty useless without registering thep hone?

Why do people buy them outright from indepedent dealers?

[Candylin]

In many countries, the phone and the sim card are sold seperately. You even can buy more than one sim card for one phone. Which sim card you buy, you choose that carrier of this sim card.
Maybe we need more info about that....

[pirky]

If your cell phone memory is too small to store some information(numbers,music files and others),maybe you can buy a SIM card to expand the memory