They are writing for an American audience.

I'd like to see a browser automatically translate units, perhaps with an extension like [1], but ideally with standard markup. That could also end the mess of brackets on English Wikipedia.

[1] https://addons.mozilla.org/en-US/firefox/addon/automatic-uni...

Well, they shouldn't. The international audience is much bigger.

You do realize that it's only "obfuscating" if you can't perform basic arithmetic, and that there are several countries that use imperial measurements?

Yes, the US, Liberia and Myanmar.

All the countries that have been to the moon, and more!

As Tom Lehrer famously sang:

"And what is it that will make it possible to spend twenty billion dollars of your money to put some clown on the moon? Well, it was good old American know how, that's what, as provided by good old Americans like Dr. Wernher von Braun!"

Cute, but most of the former British empire (including Britain itself) still uses parts of it.