Good enough is good enough for the majority of the market. They don't want to hear Vienna Philharmonic's third violinist breathe, they want to listen to autotuned pop music on a pair of $20 headphones and get on with their day.

I subscribe to Tidal, which has master quality recordings. One’s headphone choice is orthogonal to the music player you use, so if you can pick a very high quality one for a standalone MP3 player you can use that same one with your phone.