Disclaimer, not in the mechanical engineering field. That's said, its ironic that you use "actual engineering" as that "actual" bit is why, as I understand it,

Disclaimer, not in the mechanical engineering field. That's said, its ironic that you use "actual engineering" as that "actual" bit is why, as I understand it, engineers primarily use imperial units in the US—most people who do the making know imperial. I can't speak for every industry, in fact I know machinists make plenty of things in metric, but that is my understanding from talking with Engineers here.