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?
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.