Because it's not the biggest file in the media shop. That's one of the minor issues with videoes.
Someone once asked me why some of the videoes weren't encoded with the latest DIVX codecs and what-not (for size and quality), but it's a much bigger pain in the butt forcing people to download the latest decoders, and in some cases will not work with their computers. The videoes as they are now get the least amount of complaints in terms of compatibility. |