Need I say more? Yes, I suppose I do. Believe it or not, The US formally made it legal to use the SI system in 1866. So why isn’t being used? Habit and cost; the usual impediments to progress.
Of course if you take into consideration the costs of errors due to conversions and using mixed units (see the Mars lander) , then the cost of moving to the world standard is cheap. Habit is harder to combat. Until you actually start using it.
Working in the shipbuiding industry I am pretty used to working with mixed units, or at least to different designs using different systems. The advantages of the decimal system are clear in all the calculations we normally do. Consider a simple case:
1 foot + 1 1/3 inches = ?
10 cm + 22 mm = ?
Which was easier? And how many of us have had trouble at home with measuring with tape measures; calculating centers, adding measurements, converting, etc. I know I’ve screwed up more than one project because of this. On the other hand, my airplane project is almost entirely metric, in mm, and even though it isn’t the system I grew up with, it is so much easier that I can’t really imagine going back to English measurements. Only bolts (SAE sizes) and aluminum sheet thicknesses are in English and these are necessary since these are only widely available in the US in the English system.
Cost aside, it would only take one generation for the SI system to take hold. We are in a global society now, we need to get on board and stop thinking that we are special cases.
What do you think?
BTW, according to Wikipedia, only the US, Liberia, and Myanmar don’t have the SI system as their official measurement system. Aren’t we in good company.