Software as a service is good for users

When selling subscription software, a publisher needs to continue to prove the value of thier software, or users will not renew their contracts. This is very beneficial to the users and to the publisher.

By contrast, if a publisher uses a one time purchase option for thier software, they can’t get additional revenue from an existing customer (because app store physics don’t support paid upgrades). This means once their existing user base is much larger then the additional users they are likely to aquire, they should (from an economics perspective, assuming they use the one-time app purchase business model) stop investing in the app, and focus on a new app.