Why doesn't Xinhuang belong to Guizhou?

Xinhuang County belongs to Huaihua City, Hunan Province, located in the west of Hunan Province, bordering Guizhou Province. However, Xinhuang was not included in Guizhou Province, which may be because Xinhuang's administrative advantages are outdated, unable to replace Yuping Dalong's position in Guizhou, and lacking the support of a medium-sized city in eastern Guizhou. Therefore, Xinhuang has not become a part of Guizhou Province.