All I can think of when I read this thread is marley's signature quote about your father's hand-me-down anger.

Now, to address the issue at hand:
A lot of products and materials here are built on a standard of feet and inches, and as we all know, that system does not convert cleanly into metric. So, to convert to the metric system would be a long and arduous process of weeding out everything from those currently in production to those produced but not yet in use. Otherwise, these companies would suffer a severe inventory loss, and we can all agree that we can't afford that right now.
Sure, we could do it, but frankly when it comes to domestic operations, it's just not worth the trouble.