Spotify generated will generate close to 7-8 billion in revenue this year, which is more than UMG.
They are on an offensive growth strategy campaign, fighting to retain and increase their market share. Getting dumb offices, purchasing companies, getting top employees and on. Twitter just turned profit for the first time ever in q4 2016. Spotify's loss is even increasing, because money is cheap and it's a good time to make serious investments.
When they get comfortable, they will start generating profit. It's not as if companies are valued to $13bn by banks and investors if they don't think that they will get a positive return from their investments.