They wonder why they are going broke. We bring it 90% of the way and they can't take it the last bit in a timely manner. Chances are almost certain that they are already going to these houses so sort time is really all that's needed.
Look at the pace they work at, it's the most insufficient system ever. If you have one of these on your route or have delivered to one, next time you're there look at the employees that are working and how fast they are not moving, absolutely no sense of urgency! UPSer's are programmed to move at a rate and be productive and multitask.
Also look at their dispatches. At the post offices I've delivered to, all the package car routes make 3 trips. Once for express mail (sort of like NDA, I think it's time committed), then they come back and grab bags of mail to distribute to mail boxes so mail men/women can grab them when they are walking their routes, and then they come back again to for parcels and finally distribute that.