[avar]

Yes, why wouldn't it work like that?

If a package falls off a truck in front of your house you can pick it up and inform the authorities, who'll in turn inform the owner.

If the police or owner care enough to pick it up they can have it, but presumably there's cases where they can't be bothered, then it becomes abandoned property and you can keep it.

Just because you find abandoned property you don't need to go out of your way to mail it to the owner, just inform them and they can come to you.

The "why not just leave it?" aspect of this is easily defended, if the package e.g. contains electronics they'd be damaged by exposure to the elements.