[structural]

Amazon uses USPS for large cities as well (where package theft is a very big issue) - most homes have a secondary lock with access to the foyer, and postal carriers have the key. This functions just like blocks of lockable mailboxes that are found in condo/apartment complexes, but for packages.

Needless to say, the overnight/next day delivery options that you'll see for suburban neighborhoods are nonexistent in many other places.