Most subscription based music services require an internet connection for you to be able to play music, which is not ideal if you are living in a rural area without good connection. Using mobile data instead to play music can cost a lot of money because streaming music takes up a lot of bandwidth. This is why Spotify's offline services are so useful. If you pay for Spotify Premium, you can create playlists that you can download onto your device, meaning you can listen to music even when there is no internet connection. The amount of playlists you can download has no limit as far as Spotify is concerned, and only depends on the amount of storage space on your phone or other device. You can also download a wide range of podcasts to listen to offline, if you don't just want to stream music. Additionally, Spotify offers a free trial for Premium users so they can see what it's like to use offline mode and download content. This means they have time to test out Spotify's features and see whether it's suitable for them before they purchase a subscription.
You can only download content to listen to offline if you pay for Spotify's Premium service, meaning you'll need an internet connection in order to play songs if you use their free service. Nearly all music streaming services now have the option to download songs or playlists offline, therefore Spotify is not pushing boundaries with this feature.