“iOS apps” are not an industry. “Smartphone apps” are. You can always go to another store, e.g. get an Android phone. Spotify is not obligated to distribute on

“iOS apps” are not an industry. “Smartphone apps” are. You can always go to another store, e.g. get an Android phone. Spotify is not obligated to distribute on the iPhone. They are not being locked out of the industry by choosing not to distribute on the iPhone.