Or if that's too much of a disruption for users, just requiring the current device to delete it would cover most cases and be better then the current situation.
Users can set each device to automatically download and install newly-purchased apps.
Imagine the case where there is a device you have misplaced (or given to a relative, or had stolen, or ___). You must find every device with auto-download and purge the app from each one before requesting a refund.
So you create a situation where it is possible that the user quite literally can't comply with the terms of the refund.
Perhaps a compromise would be to
1. Delete from the current device; and 2. To verify the status of each app during OTA updates (which, by definition, have connectivity to Apple's servers). Any refunded apps would be greyed-out or something.
Uninstalling an automatically installed, never-opened app is not a breach of the personality of your device.
Why would you want Apple to have access to everyones online/offline usage habits for apps, and scans every time you restore a backup?
Why? Apple controls the OS, and can blacklist any App they want. They dont need to know whats installed on your device to prevent it from running.
Want a refund? Awesome. Delete the software from your phone. Then, go to the appstore, find the app again, and click 'request refund'. If apple wants to improve the user experience, they can offer 'request refund' when someone uninstalls a recently bought app.