Well, they do sometimes but not very often. Left turns cross traffic, which wastes time and causes accidents. So UPS routes are designed with mostly right turns...three rights make a left, you know.
UPS engineers found that left-hand turns were a major drag on efficiency. Turning against traffic resulted in long waits in left-hand turn lanes that wasted time and fuel, and it also led to a disproportionate number of accidents. By mapping out routes that involved "a series of right-hand loops," UPS improved profits and safety while touting their catchy, environmentally friendly policy.
I wonder though, does this make the drivers unhappy?