I remember burning numerous mp3 discs to maximize the portability of my music and lessen interpersonal conflicts when I am bound in a place with booming music that I do not like. Most audio players do not play them though, like your ordinary cd player in your car or your discman. It would also be tedious to go through five hundred songs in your discman when you are on the go.
When the first mp3 players came out, I almost fell to my knees to worship the sky. One gigabyte of music matched with utter portability. Most of them were not only meant for music, you can also store data files when you plug it to your computer. It is a storage device and a personal music player all in one.