The most popular audio format for music has had its longest time. Even the inventors of the mp3 format think it's been nice. The Fraunhofer Institute reports on its website that they no longer support mp3. In concrete terms, it means that they will terminate certain licenses for mp3 patents. The inventors believe that there are better alternatives to music today.
The official statement of the Fraunhofer Institute states:
Although there are more efficient audio codecs with advanced features available today, mp3 is still very popular amongst consumers. However, most state-of-the-art media services such as streaming or TV and radio broadcasting use modern ISO-MPEG codecs such as the AAC family or in the future MPEG-H. Those can deliver more features and a higher audio quality at much lower bitrates compared to mp3.
Twenty-two years ago, mp3 was first declared dead before the format became popular. Since the 90's, it revolutionized digital music, especially because of the easy distribution of music without DRM and the fact that all music players supported the format. Part of this, the iPod became the most popular music player for the mass: many music tracks matched and if you did not find it (or did not want to pay for it), you downloaded the songs yourself.
At the end of the 80's, Friedrich-Alexander University in Erlangen-Nuremberg began researching the music format for the first time. Researchers at this university, together with the Fraunhofer Institute, developed the mp3 format. This took only 10% of the original file size, a huge leap forward in that time. However, it did not matter at first - until software appeared that consumers could rip their CDs on.
Ten years later, mp3 became the standard for exchanging music. There were programs like Napster and Kazaa where you could download the latest albums. As a paid alternative, Apple developed the iTunes Store, where you could easily purchase albums and songs with one click. Apple chose AAC, not for mp3. This format now appears to have the longest breath and the main advantage is that you have better sound quality at the same file size.
Nowadays, the music format is no longer so much because most people listen to music through streaming services like Apple Music and Spotify. Real music lovers prefer lossless formats, of which Apple also supports its own variant.