Gmail, Drive, and Calendar all probably share a decent amount of backend data despite them all sharing some backend data as part of the G Suite, and the main Facebook app has almost a superset of the data in Messenger app (the only thing I can think of that might be missing is the "stories" stuff in Messenger, but I also don''t really know anyone who uses that). While Spotify doesn't have anti-trust concerns like Facebook and Google (at least right now), I'm a bit skeptical that there's any worries about having a combined G Suite app or merging Messenger back into Facebook proper being that much of a monopoly concern given how entwined they already are in the browser.