Yes they may save money doing this, but when you do that follow your driver for your delivery thing they just came out with, It looks like your driver is on crack the travel patterns make no sense. No order. They are all over the place, similar to how Delta does connecting flights.
Worth mentioning that many drivers will be self-employed and have no such software. UPS seems to give all drivers a software with a route to follow, many others won't bother (as they pay the driver by delivery).