Probably because Zayn's banshee vocals. Taylor is the only redeeming factor in this song. I still wish she went with a different male vocalist.
No need for another male vocalist. He just needed to sing this in a lower register. He is a very capable male vocalist but he keeps insisting on singing in this pitchy and gratting falsetto far too often.
Zayn's name is first. Why won't he push it to be released on Spotify? Ugh
Because Taylor co-wrote and co-produced it, and it wouldn't surprise me if she owned its publishing rights too. Taylor and the 50SOG team have more say here than Zayn!