The real reason...
Apple uses slot load 9.5mm optical drives. Guess what? There is no Blu-Ray 9.5mm slot load drive available in the market! As soon as one becomes available, Mr Jobs will suddenly change his position. This just goes to show you the kind of guy Steve is. If he doesn't have the feature, he does a slight of hand and downplays it, until he supports the feature, then it's better than sliced bread.