That's very insulting. No one "needs" anything much beyond food, water and air. But as enthusiast photographers, we want good photos, and we want good products to capture them. By the same token, I don't NEED a Retina Macbook to type this message on, but I sure enjoy using it.
And of course the camera doesn't make the photo, but it does take the photo. And unless all you shoot are photos of the Grand Canyon at mid-day from a tripod, to take a usable photo, it must do two things accurately and consistently... auto focus and calculate the correct exposure. The latter is pretty much a commodity, however, the former is anything but a solved problem in low light or with moving subjects.
The 5DIII has one of the best auto-focus systems on the planet - nearly identical to the 1DX. So, anyone that want's more of their pictures in focus under less than ideal circumstances should want that.
It doesn't really matter if he or I have any justification whatsoever, but the fact is, there are plenty of good reasons to want the 5DIII whether you're a beginner or a seasoned National Geographic shooter, and they are not just pixie dust.