Microsoft to discontinue Groove Music app, transitions Music Pass customers to Spotify14
The reason is simply to deduct, and even Microsoft admits in the announcement that its service hasn't been able to meet customers' demands. The competition was tougher and Groove Music was becoming slowly completely redundant on a market that's already becoming pretty crowded.
The good news is Microsoft is expanding its partnership with Spotify to allow Groove Music Pass customers to move their curated playlists and collections directly into Spotify. Additionally, they may be eligible for a 60-day free trial of Spotify Premium.
It appears that Microsoft will continue to update the Groove Music application on all Windows devices to support playback and management of owned music, but only until December 31, 2017.
It's also worth pointing out that Groove Music Pass content will be available to move to Spotify until at least January 31, 2018, so, theoretically, there's plenty of time to put all your music affairs in order before the deadline.