In an unpressurized cabin, why is the cockpit ambient pressure lower than the outside pressure? As I study for my IRA written, this (VFR) question resurfaced and continues to irk me. The annotations cite the Venturi effect as the sole reason, but I don't follow.

From Wikipedia: "The Venturi effect is the reduction in fluid pressure that results when a fluid flows through a constricted section (or choke) of a pipe"

Do we consider the parcel of air in the cabin to be the fluid moving through the constricted section of some imaginary/abstract pipe? If so, why? Can anyone shed more intuition on this?
The air moves around the fuselage, which causes a localized increase in velocity around the aircraft.  This increase in velocity causes a slight decrease in the outside air pressure, which effectively sucks air out of the fuselage, making the cabin at a slightly higher pressure altitude. 

The effect is localized.

While the reduction in pressure, and increase in pressure altitude inside the cabin is small, many GA aircraft display a 40 foot or so difference in pressure altitude between the alternate static port (inside the aircraft) and the pressure altitude with the factory static port.