It's kind of not important because nobody measures the kinds of things that require the level of precision applied to the kilogram definition using pounds.

I was about to argue that the illegal drug trade might be a counter-example, but haven't they gone metric, too?

Even if they did use the imperial system, no drug dealer is going to care about a change in the 8th decimal place of the definition of the pound.

Carfentanil is LD50 at 0.05mg. Don't be Bill Gates, 640KB is not enough for everyone and the 8th decimal of the pound is a lethal dose of Carfentanil.

Wait no this doesn't make sense. It's not an 8th decimal of a pound, it's an 8th decimal of what you're measuring. If you're measuring out a pound of Carfentanil you might be off by 0.05mg, but if you're measuring a dose you'll actually take, you won't.

It still stands that a LD50 of Carfentanil is able to be estimated away because of the change in the precision of a pound.

I stand corrected! Thanks.

It could come in handy too know one day! :/

It's ounces, grams and kilos in that business, but the ounces are an old-school unit that's dying out. You might buy an "ounce" of weed, but an ounce of cocaine is ridiculous unless you're Charlie Sheen.

An Eight-ball is an eighth of an ounce, and it's still one of the most popular ways of asking for coke. It's not really dying out as much as you say.

Would be more important if the pound had an independent definition - suddenly, a lot of international trade and unit conversion apps are affected.

Indeed, all of the US units are defined in terms of metric standards. There is no standard inch.