@Bawabus: Well, yeah, because you want the focus to be on the lead singer, and looking indifferent generally creates this by making the other members seem less interesting, which it clearly does here.
Remember, when taking pictures for album covers you must look indifferent to having your picture taken--unless you are the lead singer. This indifference can take many forms: looking off in a different direction, sneering while looking just to the side of the camera, looking bored with life, etc., etc.