I imagine this depends a LOT on your specific age and what you were doing in the 00's when MP3 player usage peaked.

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.