I think you are mixing up two topics here. There are two entities called Package, which mean very different things:
Packages in ARA cannot be deleted as long as they are referenced by a deployment. If you delete all executions with the DBCleanup Utility, you should also be able to remove a package.
Packages and Action Packs which are installed via the PlugIn Manager or Package Manager can be deleted via the Plugin Manager or Package Manager again.