There are times where the subject of a photo is "outshined" by the distracting background and thus failed to bring out the feeling that the photographer meant to portray. To ensure a subject is really outstanding, the colour must be contrasting enough and the background must be blur enough to make the front subject really seems outstanding. With photoshop, you can literally bring any subject out to make viewers focus better on the intended effect.

I had helped to cover for an basketball competition organised by one of my close friend in NUS sometime back last year. There is this really interesting photo that captured the expression of this guy in "total despair" when trying to block his opponent shooting a basket.