Although, to be fair, British people say that too, especially when Britain joined the EU. “You mean I have to stop measuring the produce I sell in pounds and ounces?!”
And, of course, they still use MPH. I imagine there would be a massive uproar if that got changed.
British have gone much further with metrification than the U.S. but there’s still way too much resistance. And some of it is very silly indeed- weighing yourself in stone, which is a rather arbitrary 14 pounds.