AAC was released in 1997, why they start to advocate AAC after MP3's patent is expired? I thought they state "MP3 is dead" just because its patent is expired,

AAC was released in 1997, why they start to advocate AAC after MP3's patent is expired? I thought they state "MP3 is dead" just because its patent is expired, while AAC isn't: http://www.via-corp.com/us/en/licensing/aac/licensefees.html http://www.via-corp.com/us/en/licensing/aac/licensefees.html