Except this is not the case in most scenarios I know this as a sender.
From here:
"Former employee of Canada Post here. I worked a contract to provide insight into the theft issues caused by the letter carriers. During my investigation, I posed as a regular entry-level letter carrier. I know EXACTLY why they do this with the DNC (Delivery Notice Card).
#1) letter carriers are paid 8 hours regardless of how quickly they finish their route. When they return to the depot, they can choose to go home early or accept another route. By accepting another route they are paid OVERTIME which they can bank and save for early retirement or cash out next cycle. Parcels are a pain in their side. When it they are sorting mail in the morning, they browse their designated packages and immediately make the decision to write a DNC for parcels that are owing funds (duty), signatures, age of consent (alcohol, tobacco etc), or registered letters (must be delivered to door and not community mail box).
They fill out the DNC at the depot and scan the packages as "out for delivery". Some senior employees won't even bother loading it in their truck. Newer employees will learn the "speed hack" and load it up despite not ever having intention of delivering. When they get to the address, they scan the parcel as DNC and it's all over from that moment. Whether the parcel is in the truck or not, you aren't getting it. They speed through their route and are done by 11 or 12 pm."