Well currently it would be royalties from licensing it out (the patent is expired so it's technically not needed anymore). There is also a benefit since consumers are more familiar with the word MP3 as opposed to AAC. However I think marketing in the past is much more relevant. I have heard of "MP3 players", but not "AAC" players.
> I have heard of "MP3 players", but not "AAC" players.
Because the latter are called "MP4 players" and the files are meant to have ".m4a" extension. Also because dedicated media player devices stopped being something ordinary people need (because smartphones) sooner than MP4 became a thing.
