I see that there is a big unification towards the "millibit" terminology, but I think that is too confusing for the average person. In the united states, we have resisted switching to the Metric system because "it's just too damn confusing." (which is insane, because inches and feet are arbitrary. We should have switched to the metric system ages ago.)
Maybe the average person in US. But fortunately, everybody else uses the confusing metric system and since bitcoin is a global currency that just seems fair. Besides, you don't have prefixes in imperial system (at least afaik) and no one wants to own 50 foot bitcoins.