I notice a tendency to feature the same Africa countries on SSC. I never see anything on countries like Malawi and Zambia for example. Any reason why?

Malawi, small. Possibly doesn't receive as much FDI.

Zambia, large in the mining industry. Most projects probably related to it.

To be honest, only around 10 or so countries (not including forums dedicated to countries) out of 53 in Africa have their own threads, so essentially not that much coverage of the entire continent meaning no news on projects. :)