I love how you mischaracterize it. All measurement systems are as artificial as Esperanto. So that analogy is meaningless here. But as far as popularity goes, the SI system is like English and the imperial units are like Esperanto. Never mind the age difference. So you're better off choosing the system that maintains consistent prefixes and units without arbitrary conversion constants. And that's what the rest of the world does. Meanwhile, enjoy the company of Myanmar and Liberia!

I don't understand why this is being downvoted. I would love if metric were used universally, but I don't really see any difference between that and wanting a single language to be used universally. In fact, the cost of different languages is certainly much higher than different systems of units. Converting between systems of units is just trivial arithmetic after all.

Because SI units are part of the language of science and communicating about rockets involves the language of science.

Also, SI units aren't some niche idealised standard like Esperanto, they're more widely used than the English language...

Because it is a false dichotomy.

False analogy, in fact. The explanation is in my direct reply to the commenter.