Double Click the Home Button

This isn't a complaint about the new double-click feature of the iPhone's home button to bring up iPod controls or phone favorites. I love it. It's tremendously useful. But, I'm wondering, why stop there with one button? It seems like the whole concept of the iPhone and its one button was to move toward a different way of doing things that didn't involve mashing a lot of buttons multiple times? Why not add more buttons so the home button doesn't have to be clicked twice? There's plenty of room to the left and right.

Now, let me be clear, I don't want them to add buttons. But what exactly is going on here? Why are they adding functionality to buttons? There's a button on the cord, the volume rocker on the side, the sleep button, and the home button. That's four buttons, and there's also the mute switch on the side. It just seems odd.