It's not good looks per se - they help, obviously, but good looks don't really denote how photogenic someone is. It's usually more to do with confidence, the ability to stare down a camera and give it emotion, and a mastery of the little tricks that make someone look good on camera (lips faintly apart, chin forward, shoulders back, eyebrows slightly lifted, eyes slightly focused down the camera lens, etc etc etc).
That's why a lot of people, myelf included, photograph better when they're taking a self-portrait rather than someone else taking the photo - it's easy to be confident and remember all the little tricks when you're holding the camera, but much harder when someone else is taking the picture.