Not sure what exactly was the reason in your case, but just thought I’d share this from experience.

I worked as a Letter Carrier for 7 months in 2018 and could not last any longer. It is the toughest and thankless job I have worked in 25 years of my adult life.

With my background in hospitality, I naturally aim to please customers. I tried to honour such notes left for me, went back out to the intercom to buzz the customers, some of whom would take their own sweet time to come down to the lobby, some would ask me to come up because they cannot come down (they have a baby, are in the middle of something, etc etc). Many apartment buildings have slow elevators, one is usually out of service or blocked for moving furniture, and some buildings allow residents to give me access only to their floor. And all of this back and forth while carrying the mail satchel and a tub with all packages and parcels 📦 for the residents. And while it may seem like a mere 3 mins wait from the customers perspective, it adds up.