The thing is the postman has permission to come on my property to deliver the mail. Stopping a mail van involves the problem of the driver. A drone buzzing around with potentially a valuable payload in it, no human to worry about.. easy prey with little consequences if it goes wrong. it doesn’t matter if it’s flying at 100 kts, 1 shotgun pellet into one of the blades spinning at very high RPM would be enough to bring it down.
like I said above drones have their place without a shadow of a doubt but not convinced they are necessary for delivering packages to houses.