It’s okay for non-demanding music but even at high bit-rates there are types of sound (e.g. cymbals) which it can’t reproduce well. Smaller, better sounding files are usually going to win and indeed they have for the most common ways people listen to music.
Isn't V0 MP3 basically indistinguishable from lossless, per a bunch of abx tests from the guys at hydrogenaudio (surprisingly even slightly better than CBR 320k)? Sure aac can achieve perceptual transparency at lower bitrate, but compressed 320k is still a lot cheaper storage-wise than lossless, and if you're limited to what's available then it doesn't make sense to turn it down.
Not for all types of sound: I mentioned one of the common problems with sounds which ramp up sharply, which is not something VBR can solve. AAC also has pre-echo issues (all DCT-based formats do) but the designed was improved to reduce them since this was one of the known problems with MP3 which you couldn’t just throw bandwidth at.
My larger point was simply that most services use AAC now because it saves them money, fits more music on your phone, and has better sound quality. MP3 is good enough for a lot of things but there’s no point in supporting two formats when both are widely supported and one of them is better across the board.
I don't disagree that AAC is better, but other than iTunes most people buying from the stores mentioned on this subthread are buying MP3 (if not lossless).
Perhaps - I haven’t bought MP3s since the 2000s since sites like Bandcamp almost always offer lossless or AAC — but I was also thinking about how almost all of the streaming services use AAC, too, and that’s a huge chunk of people’s listening.