...in fact, it's so much a better solution that I can't imagine Amazon hadn't considered it. They could easily sell Amazon Qubbies with the same pitch they're making here. I can only conclude that the real goal is to get you to install those cameras.
Side-anecdote/thought: I used to live in a mixed-use building with 20 units, or so. One of the businesses downstairs was a DVD rental place (this was only a couple years ago; they're still there!), and they volunteered to accept packages for the upstairs residents. Little informal services like that can add up to something that can't be replicated by all the technology in the world, and I worry a bit about the consequences of seeking to obsolesce them.