Because they have a lot of problems, don't know the culture and they normally have fucked up values because they only have one way for survival, it isn't based around an autism mind game, even more when you cannot measure it perfectly, even more when the IQ was taken by a shitty study of 100 people (aka. Lynn, there isn't any new studies around IQ in africa and the ones which didn't picked retarded children or kids who didn't speak english with english tests are very scarce) and they have all of the problems of malnourishment and many other things, a good example in africa is a place like gambia, there's white people, but there are more blacks by a long mile and they help eachother, which makes a good economy.
My problem isn't differences, but trying to explain them on a retarded way and trying to do a lot of retarded assumptions or studies with specific values you can have.
Even then, that study was made in the US, where i explained the cultural aspect and why everyone there uses their race, when you have no culture you will pick the next best thing, even if it's retarded.
That's the reason you shouldn't see everything with an US perspective, it will fuck you up on the long run