I actually find where I live @agentdaisy that the couriers knock every bloody door until someone answers. I live at No 12 Church Close, and I have seen a courier try to deliver to No 11 (opposite me.) When they get no response (cos they're not in!) they knock at No 9 (next door to the one they are trying to deliver to.)
Then when no-one answers at No 9, you can see them looking around to see if they can spot someone on a driveway, or in their window. So then they try No 7, and if THEY don't answer, they start walking across to me and Numbers 10, 8, and 6...the neighbours opposite Numbers 7, 9, and 11.
In some instances, I have seen them go to the road at the end of the street - 2 minutes walk away, and start knocking on THEIR doors to try and deliver the package! I was asked the other week to take a package in for No 5 High Street, which is around 300 yards from my home, in another street, around the corner. I have never even MET these bloody people. I said no.
I get that these couriers have a quota to deliver, and I know they are busy and poorly paid, and maybe they get a commission for every package delivered (and not sent back to the depot.) But knocking on every door until someone answers and takes the package in, is a piss take. And it happens a lot where I live.
There are a few elderly people in my cul-de-sac, and a couple of vulnerable adults, and I have seen couriers banging on doors and windows to try and get them to answer, to take in a package that is for a neighbour 6 doors away who they don't even know. It scares the shit out them, because they are not expecting anyone, and it unnerves them for the rest of the day!
disclaimer, none of the addresses I mentioned are real.