iPhone camera

I dont understand how this tiny camera lens from an iPhone can take such amazing pics, if we compare the tiny lens on the iPhone with the lens of a professional camera, which can cost several thousands, why are they soooo different?.
If the secret of the iPhone picture quality is in the optical detector/chip...then why do we need such large lenses on a "normal" SLR digital camera? why not put the same high end chip on a camera and get the size down? anyone??

 

Big lens brings:

- better distortion mitigation
- due to aperture it gathers more light and works much better in poor/various lighting conditions and contribute to short exposition
- better angular resolution
- larger/adjustable focal length