Can we please stop linking to this whenever there's a discussions about a new standard? There are other reasons for creating a new standard besides unification of the current standards.
There is literally 1 billion possible reasons why that could be. Smaller size. Higher bitrate. Simpler format. Faster/more power efficient decoding. More than 2 audio channels. Separation of single tracks within a song (so that e.g. you can mute vocals). These just off the top of my head.
