Most M, A and B roads in the UK (highway=motorway, trunk, primary, secondary) have a signed number. Occasionally, some roads are missing their numbers on signage from adjoining roads. It’s very rare for such a road to be completely unsigned, though it’s more common in urban areas as has been observed here. Though most people don’t refer to roads by their numbers in everyday usage, people who are using navigation services like the ones offered on OSM should be able to see road numbers since it helps them navigate more important roads like the types mentioned above. It’s only situations like these that one could argue that a road number actually confuses people trying to navigate a busy urban road with traffic restrictions that prevent most users from using it if they’re driving a private motor vehicle.