The film was shot in widescreen, as it gives a wider perspective.
Putting the film into 4:3 Pan-and-Scam mode takes away from the picture, by up to about 40% in some cases!
This is especially bad if there is something that is happening on the edges of the screen, as well as in the middle, as stuff will have to be left out.
There are some websites that explain it between than I can, but I can't find the links at the moment.
It's basically because it's how it was filmed, and staying true to how the director wanted it.
Confused
Editted for speeling mistakes 