Why do I require an internet connection to listen to downloaded songs?

[frobalt]

Right, I've got a spotify premium account and have downloaded my songs to the device, yet when my phone loses internet connection, I am unable to listen to music.

Not only does this stop me choosing a song (Can't even see them), but it also cuts out songs mid way through.

Since I'm paying premium and have downloaded songs, I see no reason why this should be the case.

Is this a bug or intended? (I know that might seems like a stupid question)