What you're saying is that our vision system is basically reframing the events seen in our entire field of view.
Movies and photographs do the same - but by choosing a certain framing, they can narrow down the possible interpretations considerably, so the viewer's perception of events will be what they intend it to be.
Watch this video from 4:10 for a very good example:
http://vimeo.com/107779620
Also notice how the characters are placed in the frame, how they start to cross the middle line, where the empty spaces are located and so on. This is subtle information and most people won't notice it consciously but their perception of the events is greatly affected.
A 4:3 aspect ratio encompassing the whole scene could not create the same impression of the relationship between the characters. Divided in two, you get pretty tall sub-frames; divided in three, it's only slivers. Widescreen has the advantage in breaking down into more balanced parts.
There's also a nice blog somewhere about the work of Roger Deakins, one of the highest praised cinematographers, I suggest reading about his work too.