Because of the lack of development .
Countries in South Africa are mostly third-world countries and are not developed enough. They also don't have good knowledge on how to use their resources to speed up their rate of development . Other factors like malnutrition, lack of healthcare and education, poor employability skills contribute to Africa's poverty.
In North America, the countries (especially, USA and Canada - the 2 main countries) are really developed and have good education, healthcare facilities, resources etc. Therefore this region stands superior to Africa in terms of development.
