You already answered your own question, but it's mostly related to higher audio quality and owning your own music, while not being bothered by availability of internet.
You don't need special standalone devices for that. Any Android phone has that. Is it impossible to listen to your own audio without internet on iPhones?
A lot of comments about the internet availability. Living in Northern Europe - never a problem. And as for lets say a flight, you can download spotify music.
Audio quality i do agree that spotify kinda sucks
> Living in Northern Europe
> internet availability
Implying that Germany is not part of Northern Europe.