Shawn Blanc says it perfectly and simply, as you’d expect:
One of the reasons I spend my money on Apple products is because they’re innovative, cool, capable, and delightful. But also, they hold their value and their usefulness for a very long time.
My iPhone 4S is over two years old. It’s never been in a case, and I carry it everywhere. I am usually careful, but two years of constant use has subjected it to drops on tile, hardwood, stone, and even a brief dunk in a stream. While it doesn’t look brand new, I don’t think you’d expect this abuse. It works perfectly, and that’s a valuable quality.