Because owning music and paying once, is way better than paying every month and listening to the same popular tracks again and again.
Yes I know, Spotify has tons of tracks available, still, I like to go through my CDs and play it right away, no internet needed, no ads, no algorithms.
+1, I use bandcamp too! Works very well and you can download or even buy a media of your preference. A win win situation for the artist and the listeners/fans.