There were several different reasons why Africans resisted European colonization efforts. However, one of the most important ones was based on Africans not wanting to be exploited.
When European countries began colonize countries in Africa, they tended to use these lands purely for their resources. A perfect example of this would be the Belgian take over of the Congo. This resulted in millions of Africans being hurt, killed, enslaved, or physically hurt thank to the reign of King Leopold II. In the end, the Congo and their economy did not benefit from the forced labor by King Leopold II.