Really though, the most ardent defence of USC units is fuelled by great amounts of Copium. The US Customary set of measurements is several independent systems of measurements which often radically different origins and sometimes irrational conversions, all stacked upon each other and dressed in a trench coat. For instance, the mile has Roman origins while the inch and foot were defined separately, much later, and with a lot of regional variation. The French foot was longer than the English foot, which is why Napoleon was listed as 5'2" tall while he was actually closer to 5'9", or 1.71 m, which was pretty average for the time.

Which one of these is more straightforward to calculate:

• You are tasked with installing a rail along a 1 mile long bridge. You know you can use two half inch bolts to affix it every three feet. How many bolts do you need?

• You are tasked with installing a rail along a 1,5 km long bridge. You know you can use two M12 bolts to affix it every metre. How many bolts do you need?

Conversions within dimensions in USC require you to memorise arbitrary conversion numbers. Conversions within dimensions in SI require you to move the comma a few spots.

Besides, if the US Customary system of units is so great, why did most of the world voluntarily switch to SI units?