The problem with Aus post (from a mate who is a postie) is that 99% of parcel deliveries are outsourced to "independent contractors" at really tiny piecework rates. They get handed a full van of parcels and a day in which to deliver them. He worked out once that once you take driving time into account they have about 30 seconds per delivery if they want to get them all delivered and make enough money to eat with. If they actually get the parcel out of the van (which isn't loaded in delivery order) knock on the door, wait for you, wait for you to sign, hand the parcel over there is no way they can make their round and not pick up a bunch of non delivery penalties. So they whack a card in the letterbox and drop parcels in bulk at the post office.
Anger should definitely be directed at Aus post but to the management and their sham contracting not to the poor sap who sticks a card in your box...