Here's why:
* Nubian was the native language of the Nubian people. It was spoken in various dialects throughout the region.
* Egyptian was the language of the powerful Egyptian empire to the north. Ancient Nubia had close cultural and political ties with Egypt, and Egyptian was used in administration, trade, and education.
While Nubian was the primary language of the Nubian people, Egyptian was a significant language used in formal settings and for communication with the outside world. It's likely that both languages were taught in Nubian schools.