Having worked in construction, I think it is the last point you make that is most important. Though a 2x4 is 1.5x3.5, it is a standard dimension. In the US, con

Having worked in construction, I think it is the last point you make that is most important. Though a 2x4 is 1.5x3.5, it is a standard dimension. In the US, construction standards (lumber sizes, door frame sizes, ceiling heights, etc) are all in feet and inches. Changing them creates a compatibility nightmare. That said, I don't know of other industries that suffer the same challenge (perhaps others can think of them). Bicycles for examples transitioned reasonably quickly from English standards (e.g. 1 in. stems and 27 in. wheels) to fully metric for road bikes at least.