Everyone who works on my farm has a foot that is approximately 30cms, so it works great. If we all had 15cm feet, then we'd say you need to step off 60 feet in the aforementioned example. It is not strictly bound by the imperial system, it just so happens that the imperial system maps fairly well to what is practical in the field without any tools, so it is what we reference. I see no benefit to introducing the metric system here, despite using it in all other areas of life.