Do You Use Your Phone As Your MP3 Player?

I had a dumbphone for a long time, so when I finally got a smartphone, one of the big things I was excited about was using it as an mp3 player. "One less thing to cram in my pockets!" thought I, and I just assumed everyone else felt the same way. Any trimming I had to do to get my collection from one device or another was a joyful chore.

Then, I started to notice something odd on the train. I noticed lots of people, perhaps even the majority, would be fiddling with their smartphones but have their headphones connected to an iPod Touch. Even people with iPhones, sometimes. And so I pose the question to you: Do you listen to music on your phone? Why or why not?