Whilst you don't have to have an app and may prefer to simply have a branded web solution only, apps remain a valuable distribution and acquisition channel for publishers.
Native apps often retain large volumes of historical recurring revenue as well as providing organic discovery opportunities in the global App Stores. Branded apps also have a number of user experience benefits for in-app and 'direct' subscribers such as native, offline reading and catalogue search, push notifications and breaking news, in addition to a variety of additional advertising inventory.