Corruption, welfare states and nobody wants to work?
Just my guess
Africa is rich in natural resources but the corrupt few partake in the wealth
"Nobody wants to work" can certainly be found in some places and cultures, but "there's no point in working because your product will be stolen from you" is the much more common problem. The rule of law, limited taxation, and respect for private property rights are essential. Without them, if you produce an economic surplus, you simply make yourself a target. And those who do manage to get ahead of the game must devote much of their energy, ingenuity, and wealth to hiding or guarding their assets.
There was a South American economist a few years ago who published a paper in which he said the primary reason lie in a country's degree of protection of personal property rights.