Useless hole in iphone skin?

It’s not useless-it’s a cutout for the ambient light/proximity sensor that senses changing light conditions, and also turns the screen off when you put the phone up to your ear to talk.

Ahh, that answered more questions than I dared asking at first. I always wondered how the iPhone knew I was answering a call. Thought it was the tilt motion sensor, but secretly knew that didn’t make sense and would call for many errors.