bitcoins tx fee just to move funds costs ~20minutes to 1 hours minimum wage.
many africans learn about bitcoin. find out it isnt suitable and just use it as a gateway into altcoins which are cheaper and more suitable to transact with.
The same thing will happen in the western world when the price of bitcoin goes about a certain level. Probably $100,000 (a million?) Hard to say really, but with only 21 million bitcoins the likelihood of everyone owning bitcoins will get further and further beyond the reach of most people. Altcoins will have their place alongside bitcoin which will act as a clearing house for larger size transactions which is why in Africa bitcoins adoption is unlikely to occure anytime soon.