Why was Justin cut from Ariana's album?

when news broke earlier this year that Justin Bieber and Ariana Grande were collaborating in the studio, fans were pumped! But when it was cut, people wondered if the two had a falling out. Not so, says Ariana. "We both got busy," she explains. "We will finish it and put it out one day. We feel like we owe it to our fans to something one day."