Because it is the premiere environment for manipulating images. But I think he used pictures because that allows us to have an intuition for the kinds of analysis that he's doing, not because he's setting Mathematica up as competition to Photoshop.
As someone else pointed out, these sort of techniques could be useful for the kinds of matrix manipulations and image analysis that scientists and engineers do. Personally, I'm impressed that Mathematica appears to handle images the same as matrices. That's powerful, and of interest to hackers.
> Because it is the premiere environment for manipulating images.
.. which is already "incredibly convenient" for those who are using it.
The example in the article is a typical straw man argument. Photoshop cannot do something, not because it's weak on a technology side. It doesn't do it simply because Photoshop users aren't interested in it as they do a different kind of image processing.
> * "Allowing us to have an intuition .." *
You lost me there, buddy. I spent few years working in the image processing field and let me tell you that the clustering of image fragments by similarity is something that would interest a fraction of a percentage of a researchers in the field. And if his example allowed you to understand what kinds of analysis he is doing, I humbly take my hat off, that's really impressive.
As someone else pointed out, these sort of techniques could be useful for the kinds of matrix manipulations and image analysis that scientists and engineers do. Personally, I'm impressed that Mathematica appears to handle images the same as matrices. That's powerful, and of interest to hackers.