You hear of a "Six Pack" and "Tri-Duce" (carb setup with three two barrel carburetors) ...
Wouldn't 4x2 barrels or 2 four barrels be better?
A 3x2 setup tends to run on just the middle carb most of the time and the throttle on the outer two is only opened in high rpm operation. There isn't a need to match the number of barrels to the number of cylinders when the outer carbs are essentially just there to allow a lot more air in at full throttle and high rpm.
Some race cars do use 4x2 setups with one carb per cylinder but they are designed to run at High rpm all the time.