I never understood why people do this
It's happened to me a few times before by a delivery company.

Surely it's EASIER to knock/ring at the door, than it is to fill out a "While you were out" card?

Why would anyone spend their time doing something more cumbersome - and which is going to make people angry?
(EuroSong I love horse meat: best of all the animals, Sun 5 Apr 2009, 17:23, 1 reply)

apparently
As for speed, it's faster to spend 15s dashing off a form than waiting for the door to be answered (if at all). Since some people are allowed to finish as soon as their rounds are done, there is an incentive to rush. This is, I think, one of the "spanish practices" that is intended to be eliminated with the post office reforms.

Or it could be that the person is overworked, and has to rush to avoid pulling unpaid overtime; in which case they need to raise the issue with their employers and their union (who don't seem shy about making a fuss)

Or, it can be because they actually left the item back at the depot, or don't fancy carrying it on their rounds, or digging aroung in the back of their van for it. If you have the recipient go pick it up, it instantly becomes Someone Elses Problem.
(The Incredible Sulk Finally remembered his password on, Sun 5 Apr 2009, 17:36, closed)