Do they use drones? Or are you talking about real people? A real person can hide something away, and tell you where it is.
They are talking about real people. And no, a postal worker (Regardless of which service provider) who just "hides" packages is grossly negligent.
Here's a story: Couple months back, I bought a PS3 via Amazon. Delivery was via DHL. The idiot who made the delivery, upon not finding anyone at our home, decided it would be a marvellous idea to hide the package ...
in the waste paper bin outside my home.
Now, everything went just fine, I got the package and all, but there are so many things that could have gone wrong. Protocol for this is to first see if any neighbor is available to take the package. If that's not possible for whatever reason, the package is taken back to the nearest post office so that the recipient can get it himself.
By dumping this package in the bin, there was a severe risk of it getting stolen. There are a lot of kids in this street, lots of people goign by, one of them would just have to witness this and see a shiny big Amazon package in the bin. Or, radical thought, what would have happened if these bins were emptied on that day?
Messing with mail is a pretty big offence in most jurisdictions. Ensuring secure delivery is one of the reasons why we pay companies like DHL and UPS for their services.
Part of that is that the deliverer HAS to have positive confirmation that the package has been safely delivered to the recipient or a proxy. "Just hide it"? No, thank you.