I just had a thought that made me both confused and feel really big brain-
The term “metric shit-tons” or “metric boat-loads” etc. show how ridiculous the metric system is. If your system of measurement is so wonky that it’s used as a filler for an unspecified weirdly large amount of something, I think you’ve won the “confuse everyone” game. It’s also sometimes used as a stand in for a weirdly specific large of something. (At least in my experience)
Americans will use anything but the metric system, except for in hyperbole, then we will dunk on our own system bc we can.