I ask this question in good faith, coming from a long line of dedicated music devices, including the Diamond Rio PMP300, and a huge, file based, music collection. Why not use a smartphone?
The amp in them is slightly better than a smartphones assuming you are using wired headphones. Other than that I like having dedicated devices that do a thing as good as the thing can be done. It feels like it will never become outdated so I only ever need to continue my library of music in that one place. It's also nice not draining my phones battery by listening to music. Knowing that the device is incapable of tracking you or giving you ads in any way is good too.
I also prefer single purpose devices for retro gaming and taking photos.
Some of us don't want that level of functionality or capability. I prefer a dumb device that lacks the capability to obsolete itself at the behest of the mother ship, or analyze and interpret my behavior for ad revenue
