The standard of the Compact Disc, established in 1982, is rigorously defined. If you want to make a CD player, you read a book, you implement its design specifications, and you can perfectly reproduce the audio on every existing CD. The standard was designed to perfectly encode all the audio signals within the range of human hearing. The discs themselves are portable, stand up well to use, and last a very long time without degrading. Being a digital format, they can easily be transferred to more modern digital storage and reproduced again on the other side of the world.
Compared to vinyl records, they are a little worse for long-term archival, but considerably cheaper to produce and store and are not subject to the infinite gradation of analog reproduction fidelity. Compared to audio files on flash memory, they are more expensive to produce and store, but significantly better for long-term storage with no difference in reproduction fidelity, and benefit from implementing an actual standard that obviates the need for interpretation by software.
It is possible that we could develop a physical audio standard to render the compact disc obsolete obsolete using the technology of flash memory, but we don't have one right now and it's unlikely that we'll see it within our lifetime. We have firmly left the era where companies are willing to invest the time and money to work together to develop a standard like that for physical media - the demand for it has dried up, so we are left with the last best format.
Before someone mentions it, I know that there is an argument to be made for the humble and oft-forgotten minidisc. But I, like many others, have never held a minidisc in my life and so cannot speak to it, and so it is beyond the scope of my writing.