I presume that each batch of photos will have a specific theme or a use case in mind. If I were looking for sharp photos for my web design consulting website, and I think Apple products are the standard for the industry, I might use these images. Conversely, if I were doing a basketball design, I might incorporate urban images (asphalt, chain link fence, generic graffiti) to invoke a particular mindset or attitude.
Some people believe they become better humans for using Apple products. By showing it to the world they think that other people will agree.
It's exactly like the cross.