If you get a package in your mailbox containing drugs the police will not be able to prove that you ordered it, someone could have mailed it to you with malicious intent.
If you pick a package up from the post office at a "poste restante" it makes it clear that :
- you were expecting the package
- you took steps to hide the link between the package and you
So, someone ships me drugs without my knowledge, I receive a notice in my mailbox that I have a package, I assume its an ebay package and go pick it up. Somehow there is proof that I ordered drugs?