It is hard to answer this question for certain. However, I would posit two main reasons for the fact that Africa (or, more specifically, Sub-Saharan Africa) has not benefited as much from globalization as some other places.
The first of these is its location. Sub Saharan Africa is not as near to any rich countries as other places that have done better in this era of globalization. It is not near to the United States and Canada the way that Mexico is. It is not near to Japan and South Korea the way that China was. This means that it does not have any major economies that can act as its natural customers. This makes it much harder for Africa to progress.
The second of these is its history of colonization. Africa suffered from colonization much more than did most other parts of the world. South and Central America was largely independent by the middle of the 19th century. China and Japan were never truly colonized. India was colonized, but it was not as badly affected. By contrast, the Sub Saharan African nations were kept under tight colonial control until about 50 years ago. They were split up into countries based on lines drawn by the Europeans. These lines often created multi-ethnic, unstable populations. With these pre-made tensions and with the fact that their economies were run for the benefit of their colonizers until very recently, the African countries have been at a serious disadvantage.
These are two of the most important reasons why globalization has been less helpful for Africa than for other regions.