So, parcels meant for addresses that are farther than this radius wouldn’t get delivered… without some system of transfer utilizing multiple drones or exchanging batteries mid route. Moreover, if a drone is getting to its destination all alone it might encounter a power line on its way or come across a stray dog or cat.
Children playing on the way can also interfere with its operation and hence pose security risk as well as risk of a damaged delivery. These types of losses would be quite common if drones were used today for parcel delivery.