Sending only notifications doesn't cut it.
We as senders, want to use this app to monitor any problems happen to the parcels.
So we can report & take better action towards the courier when we notice any failure.
For example :-
"Send notification if parcels' status still In Transit/Out of Delivery for more than 5 days."
So, if its (parcel) status still Out for Delivery after 5 days, we can straight complain to courier & take action (search if lost, misplaced).