My understanding, from what I've read (I've not had a chance to speak to an Amazon driver, as I have with some other services) is it's less about the monitoring and more to do with how long they are given to deliver each parcel. This is pushed so, in cities, it can be a few minutes, so they have no option other than to stop the van as close as possible to the address, then sometimes run to the front door and dump the parcel and get straight out again. Rinse, wash and repeat.