I've missed a few courier deliveries, but my orders are too high value (and I pay extra for insurance) to ever allow safe drop, despite there being almost no chance one of the packages will be stolen after delivery. All the couriers I've ever dealt with basically use ATL as acceptance of the package as is before receipt, thus negating the insurance (for damage, in particular). There's no way I'd absolve a courier (no matter how reliable) of liability for loss / damage before I've even set eyes on the package(s). 

(Not replying to anyone in particular, just putting a random 3c into the conversation :D).