This quote from a CNN/CNET review of the iPhone makes pretty clear why there's no traditional interface on the iPhone:

Still, the interface and keyboard have a long way to go to achieve greatness. For starters, when typing an e-mail or text message the keyboard is displayed only when you hold the iPhone vertically. As a result, we could only type comfortably with one finger, which cut down on our typing speed. Using two hands is possible, but we found it pretty crowded to type with both thumbs while holding the iPhone at the same time. What's more, basic punctuation such as periods or commas lives in a secondary keyboard -- annoying.

So we're just a downloaded update away from a horizontal, punctuation-included keyboard, rather than a brand new purchase. I wonder how quickly Apple will start issuing updates.