Even UPS sounds.. not great. I have a friend who's a delivery driver for UPS and especially this time of year he has days where his truck is loaded with 250-300 parcels and they're basically all supposed to be delivered by evening. They even hire temp guys as runners who ride along in trucks to help the drivers get the packages dropped off quicker. Not only that but if they do clear their truck and they have fellow guys in their route who still have a load to clear, they tend to be asked to stick around and help take that load. But it means 10-12 hour or more shifts in some cases.
It's the Amazon/online shopping craze, and seems like it isn't a very easily scalable problem.