Take a look at these results of professional photographers using iPhones:
http://www.freerepublic.com/focus/chat/3246610/posts?page=19#19
They don’t think they need special lenses . . . and you CAN fully control an iPhone’s camera. By the way, what do you think happens when you take a video? Thousands of individual pictures are taken on a single charge. . . at 30 frames per second or more. The iPhone 6 can do it at 240 frames per second.
Video frames are very small, and not suited for print. If you're a sports photographer for example, you need to shoot several full sized photos per second for several seconds at a burst.
You need dials/knobs/buttons on the camera so you can adjust things quickly without taking the viewfinder away from your eye.
Lenses.... that's where much of the image quality comes from in great images (something one might hang on their walls, etc.). Physics limits what can be done with a tiny cell phone lens.