???
The Post Office only delivers to PO Boxes in rural areas.
In California when you get a drivers license at the DMV (Department of Motor Vehicles), you then fill out your mailing address (PO Box) so it then can be delivered to you. The DMV prints your PO Box on your license (not your street address) so it can be delivered to you.
Walk into your local sporting goods store to buy a shotgun and they take one look at your drivers license (with PO Box listed) and they say they cannot sell to you as your license must have a street address on it.
Return to the DMV and apply using your street address and when it comes to the local Post Office, they send it back to the DMV saying they can only deliver to PO Boxes!
That’s as clear as I can make it.