Drummer Lars Ulrich specifically addressed that in his announcement:
The news comes shortly after the band announced the launch of their own Blackened Recordings.
When [Sean Parker and I] saw each other a few months ago, we could see that we had been put as adversaries but we had much more in common and sitting down was long overdue. We were younger, maybe somewhat more ignorant to what was going on in the real world. When we sat down and had a heart to heart. Spotify has solidified itself not just as the leading music service, but, as far as I'm concerned, the only one. Spotify is a global entity and Metallica works on a global basis, too.