Often it is the story told by the main subject that attracts at first sight the observer, it is almost due to our nature.
But there are a lot of stories that permeate an image, there is for example the history of the place, the private history of the people in the shot, but the most important is the photographer one, how he made the shot, what he intended to communicate.
Most of all it is our history that lies beneath our photographs, what brings us to achieve them, which leads us to express something, and it is the main reason that drives us to... take photos.