Many locals hitchhike in countries throughout Africa, often paying a small fee to the driver. It is best to check the political and social climate of each region before traveling.
In the whole of Africa it is possible to flag down cars and pay them a required fee and get a lift in return. That is just the way public transport works in this part of the world - he who has a means of transportation, that is a car or minibus, is automatically expected to give lifts to others and of course charge them a small amount of money for the favor. The idea of it has nothing to do with the Western idea of hitchhiking.