Filling out delivery notices can be a real hassle when it is dark, raining, and you are trying to dig them out of a shirt pocket while wearing winter clothes and gloves.
If you encounter delays during your work day, a good use of that time is to go through your load and stick delivery notices onto any packages that are likely to need them. Its a lot easier to peel them off the pad ahead of time and write on them in the back of the truck, in the light and out of the wind and rain.
When you get to the stop, if it winds up being a send again you can just peel the note off of the package and stick it to the door without fumbling around with your pen and a flashlight. If its not a send again, the customer can keep it as a souvenier.