The United States officially converted to the metric system in 1981...
Why do they still use miles, gallons and feet 2 this very day?
The real question is, why aren't you guys on the English system? (We still blame them in the name - lol). Why add and subtract zeros when you can use 12s, 16s, 5280s, etc. And a gill is cool, I don't care what anybody says. ::/
Much of industry has already switched to metric (actually SI), except some historically stubborn industries use old units that may never be converted ("barrels" in the oilfield, for example).
The man on the street may never convert. There is a silly sentiment in America that equates describing one's height in meters with a takeover of America. I think Britain has a similar sentiment - don't they still use MPH on their highway signs? But anyone who ever had to pick up a calculator wishes we would switch.