Super selfish reason but as an architect in the US, I deal with nice round imperial numbers all day. Door frames, typically 2”. Standard commercial door, 3’x7’. All the codes are based around imperial too. ADA door width, 3’. Masonry Dimension, every 8 inches. At this point, it would be hard to remember that ADA turning radius is 1525 mm (not the easy 5’…. And yes, I know that’s changing to 67” soon). There are literally hundreds of dimensions I would have to relearn. I suppose it’s probably for the best to switch over and rip that bandaid off, but damn, it would be a headache and take me much longer to review drawings in metric (in the short term).
True, would just have to get accepted by the ICC and all the state legislatures who approve state wide code. I have a feeling it will be difficult to convince some of the less forward thinking states to accept metric codes that take into account the rounding…. Who knows though. I don’t know a ton about that side of things