From my understanding, which is not complete, as I only realave an interest in Southern African history, is that most Africans were goverened by their tribes, etc. Their formed groupings were generally quite small with very few having territory extending any significant distance. The Zulu's made one of the largest African Tribal kingdoms in Southern African history, and look how small that was. And even then the rule was quite splintered and very inneffective.
The reason it is represented however is that it was capable of rallying their armies to fight off external groups, and did have a system of local and "national" government. Something most all of the other African tribes could not do and did not have.
The choice not to represent some of these countries is appropriate in the areas were they had no significant national identity.
