Out of curiosity, what mp3 player are you using and what's your use case? I feel like I haven't seen anyone using a dedicated mp3 player in a long time.

Not OP but these are my reasons if you're interested.

I've been using Rockbox for more than 10 years and know the interface by heart (there was one occasion where the screen broke on a player but I could still use it perfectly fine, by counting the button presses) so one part is just simple habit.

There is no personal information on the device, so there is no need to lock it and for me to try and unlock it in a hurry and if I lose it it's only annoying.

I really like the physical buttons, I don't have to look at the thing to do stuff (yes, there are other solutions to this).

Battery life is usually excellent.

At the moment I'm using a SanDisk Sansa Clip Zip. Once that thing breaks I'll probably just use my streaming server (via airsonic) on my phone and yell at the touchscreen because I have no idea what dedicated player is still usable with rockbox (apart from the refurbished old ones).

I feel like part of the reason though is that all the players are attempting maximum lock in. Even if the files didn't have DRM they often don't use anything like a standard for encoding metadata.