Well it's Friday for everyone not just UPS drivers. So that college that is usually open is closed today. That shipper that usually make you wait is ready to go and is shipping half of what he usually does. Those apartments that usually need a signature are now home because they left early on friday.
All those things help the day go faster and help you get off more stops quicker. Also yes it's friday! You telling me you don't rush through things to start your weekend?
That being said I'm sure there are drivers that play the system but hell that's what management does also.