What significant things do you want africa to do in game, given it didnt achieve much in period, and locations matter less than pops (which sub saharan african will be terribly behind on)
Location density is something that people have discussed here with respect to every part of the world - from China to South Asia to the Americas. The developers have made it abundantly clear that location density is not being driven by "historical importance" or "achievement" (your metrics, clearly ill-applied in this discussion) so much as anticipated gameplay directives. This makes perfect sense when you consider the increased compute power likely needed per location added to the game.
So given location density is being driven by anticipated player preferences, unless you're also on the China-related threads talking about how little China "achieved" during the period of the game as a reason to not increase Chinese locations, I see no reason for you to be discussing that on this thread. It frankly comes across as overly dismissive at the kindest, and blatantly disrespectful at the worst. Do you think Japan, a nation which didn't successfully expand beyond its islands until the 1900s, has an extremely high location density because the Japanese "just did that much more" than China? Or do you think it's because the devs clearly like Japan a lot, expect their players to as well, and therefore have pumped it to the brim with flavour? Your guess is as good as mine.
However, if you would like to actually learn about how and why you are wrong over whether Africa "achieve[d] much in period" (which I take as your opinion on whether or not the continent has enough "going on" to fill that increased location density with content), there are hundreds of replies on the dev posts for each region of Africa, which might be a great place to start. These include detailed suggestions for how location density could be increased in Africa, as well as suggestions for how and where new country tags and SOPs could be added to the continent.. Many posts in the latter category are qualified
by their posters with an acknowledgement of the limitations placed by the current location distribution.
There is absolutely a historical merit to increase locations in Africa; it's up to whether the devs want to or not.