Erik Pancakes said:
Because it wasn't shown like that in non-IMAX cinema, and some people don't like the shifting aspect ratio.
Besides, the BR's aren't technically OAR either, as it crops the IMAX shots to 1.78:1 when they should be 1.44:1.
Yeah the blu-ray isn't, but I think the bonus disc on the ultimate collector's edition has the IMAX scenes closer to the OAR, same with TDKR too.