I lean softly towards Apple on this one. A few reasons I can think of for why subscriptions are preferred over upgrade pricing:
- The app developer can keep making money over a longer period of time.
- Generally means somebody can try out software first before committing, whereas upgrade pricing implies you either have to commit before trying it or nothing -- there are no demos on the App Store.
- Subscriptions also mean a developer does not hold out new features or bug fixes for customers unless they upgrade -- it incentivizes developers to keep working on an app and maintain a relationship with customers. This is especially true as the app needs to be updated to be compatible with new devices and OS versions.
- Potentially lets customers choose feature sets in the app. This is a good thing as it means developers can broaden their market to customers who want to pay less for fewer features or more for more features. It doesn't lump everybody into the same bucket.