I seem to remember that speed limits in Scotland are posted in MPH. In Canada they are Km/Hr. A lot of imaging stuff (both printing and scanning) resolution is described as "dots per inch" or "pixels per inch". I have done automation equipment where the underlying units were decimal inches, and the User Interface would display either metric or imperial units.
I tend to use which ever unit makes the most sense to me or to the person I an communicating with. I was involved in designing a piece of automation equipment for a well known electronics company which required that all materials be sized in metric units, so the 1/2 inch aluminum plate we used suddenly became 12.7 mm plate. What ever.