I can guarantee that these drivers are tracked within an inch of their lives and there is absolutely no allowance for parking anywhere other than the shortest distance to an address.
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.
I imagine they throw the van into any space they can as they aren't paid enough. I've seen a local Amazon delivery driver running back and forth all day long. It can't be worth doing that.
"I need this job and they don't give me the logistics to park appropriately, so I do whatever I can, knowing I'm not doing the best societal thing with where I park. I hope I'm not late on rent this month."
"I'm underpaid and have a brutal schedule so I'll take all the shortcuts". Hence their 'dump and run' delivery style. Also the large quantity of piss bottles on the roads to their depots. I can't really be annoyed with the drivers when Amazon's system squeeze every drop of work out of their drivers and warehouse staff. But, ultimately, we're to blame because we want free delivery for all the rubbish 'we' order online.