Simply bcz I like foss.I have moved to other opensource alternatives to popular apps so it was the only app that wasn’t. Also bcz I use obtanium to install apps, installing spotify meant to install using apkpure links which maybe unsafe, and if I want a modified app, first have to install xmanager.
I said that but its also true that streaming and opensource are a bad match. I tried to go full invidious and play songs via invidious client called clipous, its excellent video player but I missed spotify’s mixes and recs.
While google is just evil, but youtube is really intimidating cuz it has a lot of foss apps that can just sync the liked songs, take recs from ytm and play songs.