That's a question you are supposed to ask yourself. Well, in the case of today's shot the reason I took it is different to why it intrigues me now.
I took the shot because I saw a man up a ladder and a woman's dress on a dummy and thought it made an interesting, if obvious, contrast.
Looking at it now it intrigues me because the image plays with perspective and the picture plane. Everything in the image is presented flatly, yet when you read the image there are multiple layers: the text on the window, the figures behind the glass, the perspective of the shop interior emphasised by the shelving and strip-lights, the reflections of the buildings and people. All these elements force you to change focus, although the image is flat.