One of the big draws of Spotify Premium is that the service allows you to download music for offline listening. So if you’re going somewhere where LTE or Wi-Fi might not be available (camping) or might be expensive or slow (most airports and flights), you can save tunes to your device and listen offline. Hell, even if LTE or Wi-Fi is available, you might want to download a song anyway: if you’re one of those people who plays a track on repeat, it’s better to download a song once over Wi-Fi than use your precious data to download the same bits over and over again.
Spotify Premium allows you to download music to (up to) 3 devices. Like most software with such limits, you can log in to your account and revoke permissions for a device… in case one of your devices is lost, stolen or broken and you order a replacement. But Spotify’s UI isn’t that helpful:
I have Spotify installed on an LG G Stylo (phone), Asus ZenPad (tablet) and Amazon Fire (tablet). But I can’t tell which device is which, because Spotify’s programmers can’t be bothered to add a few lines of code to their app.