What's wrong with this picture?
"Although it can, apparently, navigate to its destination on its own it will be supervised by an Amazon employee during its trips to and from houses. Hopefully, a human presence will probably deter people from kicking the box on wheels or stealing its contents."
1. If it always needs a person with it, it's useless. You may as well have a seat for the person, carry more goods and call it, oh, I don't know ... a "delivery van"?
2. If unaccompanied—
—a. Superb theft target. Medium-sized van with a Faraday-shielded load area and a stick-on Amazon logo, an hour of patrolling on city streets kidnapping deliverybots, back to base (garage also shielded) and you've scored a nice little earner. Unless of course it's restricted to low-value goods, in which case, whater was the point?
—b. Fraud. Poorly paid Amazon despatcher lets his mate know when a £4.5k shipment of phones and gadgets is on its way, including a couple of nice ambush points ... the rest is obvious.
—c. Drug deliveries. Already mentioned by others. Who can tell at-a-glance the difference between an Amazon delivery-bot and one carrying narcotics?
—d. Terrorists. Also already mentioned? Either no one suspects the delivery-bot (before the first attack) or everyone hates and fears delivery-bots (after it), in which latter case they are removed from the streets because of hostility.
—e. Accidents. They won't be perfect and they will sooner or later have collisions with people, pets, cyclists, scooters and cars. How soon before a bus swerves to avoid one and someone is killed? The fact that this could just as easily happen with a manned van doesn't matter: people will immediately bang on about the "unacceptable risks" of bots.
—f. Surveillance, spying, voyeurism. It's not an Amazon bot that followed Gertrude down the street, taking photos of her legs—it just looked like one. It wasn't an Amazon bot that quartered the entire neighbourhood all morning hacking domestic WiFi. It wasn't an Amazon bot that collected photos of people going in and out of Babylon-on-Thames.
—g. Where's my stuff? How long before GPS spoofing, jamming, signal blocking and a ton of other lovingly crafted malware jams, confuses, misleads these bots, and goods are mis-delivered, or just missing, etc?
Will a single bot deliver to a single address per mission? If not, how do you guarantee against pilfering? What happens when the battery runs out? Who collects bots which have died for any reason? What are my rights if the bot turned left into the canal carrying my new iPad? Will these things be contending for space on already crowded pavements, or cycle lanes, or roads and streets? Will one simply stop, forever, at a busy crossing? How soon will the urban craze of spoof-a-bot (using radio, lasers, ultrasonic bleepers, photographs and GPS futzing) continue before Amazon gives up? (User 'Spanish2019' will defend his title for "Most steps fallen by a decoyed Amazon bot", to widespread acclaim. His popularity will be exceeded by 'M.Hole66' bragging of his "Deepest manhole/roadworks containing a dead bot" record.) How many will return to base in Bumfuck, Rednecksville, riddled with bulletholes inflicted by drunken yahoos? If they use pedestrain crossings/ crosswalks, how many will simply be crushed by buses and truckers who don't give a damn? (Or even car drivers, who are already hostile to vehicles marked as auto-piloted?)
(And don't get me started on the really sophisticated attacks, where Black Hats get into the despatch and routing system one day, and a dozen of them in the same city strike in the same morning, scoring £100k of stuff. It's only 50 bots with £2k of goods each.)
In sum, this idea is ripe for mischief, theft and wastage in ways which human-monitored and -run stuff simply isn't.
Even if you use it only for low-value consignments (why bother, then?) the "mischief" category is going to be a huge problem all by itself.
Like the airborne drone delivery idea, it's an attractive concept for those who think "We can, so we should" and a prize waste of time for those who instead ask "What about the real world?"