You joke, but why not? Rent a small shop and put a landing pad on the roof, which then feeds a vending machine as the storefront. That also solves the authentication problem since it's easy to require a credit card swipe or a smartphone ping to dispense the package.
Because this is a different invention.
The post office.
The post office also ought to use this technology to make mail delivery faster. Today, sending a letter across town takes days, but with drones perhaps it could take minutes.
You might even get to talk to a human while you're there!