Have you been somewhere with no internet access and tried listening to music?
Chances are you encountered the same frustrating problem I did last week.
I was holidaying with my family near Coffs Harbour in New South Wales, Australia. There was a 3G signal, but it was weak and intermittent in our accommodation. The resort had WiFi in communal areas, but that does not help when you want to listen to music in your villa.
On opening Spotify I would have to wait what felt like a minute or more while it tried to connect to the internet. Often failing. Then it would present me with my downloaded playlists.
The ability to download music is the main reason I subscribe to Spotify. For precisely these moments. When network connectivity is an issue, for example when on a train or in a car, and to limit data usage.