It was probably initially added as part of an import of US Census data (TIGER).
TIGER doesn't have all that much differentiation for minor roads, and the import didn't do anything other than a direct mapping of TIGER classes to specific sets of tags. For unnamed residential streets, it probably should have considered things like length and connectivity to downgrade a bunch of streets/roads.
TIGER doesn't have all that much differentiation for minor roads, and the import didn't do anything other than a direct mapping of TIGER classes to specific sets of tags. For unnamed residential streets, it probably should have considered things like length and connectivity to downgrade a bunch of streets/roads.