africa is a vast continent
From what some of the moderators and "Chowhound Team" have noted on several threads about new boards anywhere; my impression is that they'd absolutely love to be able to add all kinds of boards for such things but are limited by current technology and by the work involved in sorting older threads appropriately. Also by more urgent issues to be addressed. The following link answers some of it, though its more oriented at US geographical boards. It applies, I think.
slow chef, like you I find it ridiculous that an entire continent gets only one board, but the truth is, it's one of the slowest boards on chow. They're not going to give us a South Africa board until enough South African posts start showing up on the existing Africa board to suggest there is a demand (beyond the two of us!) for a country-specific board. And right now, there's maybe two posts a month.
Why don't you try get a couple friends to start posting here? If you do it, I'll do it...