It doesn't, though. I lived ten years at an address they wouldn't deliver to. I had to rent a PO Box in the nearest town to get USPS mail, whereas UPS and FedEx delivered right to my door. I don't know where you're getting your information, but it isn't true.
Your mailbox might not be at your drive way, or on your front step, but a mailbox cluster in a central location.
From the USPS (emphasis mine): > We’re proud to provide secure, reliable and affordable service to every address in the United States, plus its territories and its military and diplomatic installations worldwide.
Yes, it's a hard address which the fire department, for example, can use. And the USPS knew about it.
> Your mailbox might not be at your drive way, or on your front step, but a mailbox cluster in a central location.
My mailbox was in a post office miles away from my house, which I had to pay for. I've since moved.
> They have the legal obligation to deliver to all addresses. Do you have an address that has been assigned by your county?
While that might be true, in practicality it was not. It took me months at two different locations to get USPS to stop screwing things up or to give me access to a cluster. I think a lot of people here have had great experiences with USPS and are unable to imagine geographies where the system doesn't work too well.
That sounds similar, but is significantly different, and can be a major pain when dealing with people or businesses that believe the myth, and try to send important paperwork to a physical address, which may end up in our P.o. box if the USPS person handling it recognizes the name and can match it to a box number.
Putting both the physical and P.o. box addresses into an address block, in that order, works well, but then shippers can balk at finding a box number. (see also “Falsehoods programmers believe about addresses, etc.”)
They will deliver for every mail address. USPS designated non-deliverable addresses are typically new addresses that haven't been added, or as another commenter posted, an address that is unsafe to deliver.
Now, delivering to your mailbox might be a central mail hub that is part of your community/neighborhood, and not directly to your door, but that is still your address's mailbox.
https://sellercentral.amazon.com/forums/t/when-usps-does-not...