One aspect of the human visual system, it that once we learn what an object looks like, we tend to keep it for reference point later on. This happens with everything that we see in our daily encounters. For example, learning to read, once we know what some words look like we now longer actually ‘read’ them. This is like not seeing at all. 

By subverting the image, it forces the viewer to look again. To re-evaluate an image or place that perhaps would not be of much interest or consequence to the viewer.