There's a fine line between removing context and removing distractions, and it's completely open to interpretation. The photographer must choose whether or not the context is needed to represent his/her feelings or intentions. Hopefully the photographer knows what he/she wants to communicate to the viewer, and if the viewer is looking for something else, then the composition simply wasn't effective...for that viewer.

edit: I don't think this is necessarily dictated by the subject matter. I think it depends on the photograper's interpretation of the subject matter, and we all know we don't interpret things the same way. There are some subjects that are almost always interpreted the same way, but to say there is only one correct way is very limiting and in my opinion, that throws art out of the equation. The effectiveness of any composition is determined by the photographers ability to communicate his/her personal interpretation of the subject, not their ability to duplicate the common interpretaion.