Who?
There was about a decade there where everyone who had the slightest interest in music had an mp3 player of some kind, at least in the 15-30 age bracket.
I finished high school in 2001 and didn't immediately go to college, so I just didn't have a need for a personal music player anymore. I was nearly always at home or at work, and I drove a car that actually had an MP3 CD player. I felt no need to get an iPod.
In 2009, I started going to college, but then also got my first smartphone, the Motorola Droid, which acted as my portable MP3 player for when I was studying in the library or taking mass transit.
If you were going to school or taking mass transit in the middle of the '00s, then you were probably more likely to have a dedicated MP3 player.
1: Well my car would play MP3s burned to CDs in its CD player; not sure if that counts.