> public would expect two photos taken at same time with same model camera should look identical
But this is wrong. My not-too-exotic 9-year-old camera has a bunch of settings which affect the resulting image quite a bit. Without going into "picture styles", or "recipes", or whatever they're called these days, I can alter saturation, contrast, and white balance (I can even tell it to add a fixed alteration to the auto WB and tell it to "keep warm colors"). And all these settings will alter how the in-camera produced JPEG will look, no external editing required at all.
So if two people are sitting in the same spot with the same camera, who's to say they both set them up identically? And if they didn't, which produces the "non-processed" one?
I think the point is that the public doesn't really understand how these things work. Even without going to the lengths described by another commenter (local adjust so that there appears to be a ray of light in that particular spot, remove things, etc), just playing with the curves will make people think "it's processed". And what I described above is precisely what the camera itself does. So why is there a difference if I do it manually after the fact or if I tell the camera to do it for me?