Why is the term Chari-Nile considered obsolete in African language classification?

The term "Chari-Nile" is considered obsolete because it was superseded by the broader Nilo-Saharan classification.1

Originally, the linguist Joseph Greenberg proposed the "Macro-Sudanic" family, which he later renamed "Chari-Nile" because many of its constituent languages were located in the watersheds of the Chari and Nile rivers. However, in a subsequent 1963 study, Greenberg postulated the Nilo-Saharan family as a comprehensive "superstock". This new, larger grouping incorporated the earlier Chari-Nile family alongside other previously isolated language units, such as Songhai, Saharan, Maban, Komuz, and Fur. Consequently, the Chari-Nile designation fell out of use as scholars adopted the more inclusive Nilo-Saharan framework to describe the genetic relationships among these African languages.1