They have those systems because it would be impossible for them to implement ours. They don't have the infrastructure to support it and so they've skipped all of that and gone with a system they can afford and that isn't affected in a way that would cause others to fail. The US has the opposite problem where there are generations of people used to an old system who have no desire to change. Until they become few enough in number where the cost of supporting their business is as impractical as it would be for an African nation to implement it, no company can afford not to continue offering it without losing those customers who refuse to modernize.
We're rich enough that we can afford to keep antiquated systems in place because people are comfortable with them and value that comfort. These African countries will eventually run into the same problem where there is a new, better, cheaper way of doing things but they have an entire population that's comfortable doing things the old way and who don't want to change because they pay a cost to learn that new system. Some even less developed countries will start using the new system for the same reasons previously established.
Think of it this way. Each year automobile manufacturers release new vehicles that have more features, better safety, etc. but do you upgrade every year? America is rich enough that many people could, but most people don't. They're comfortable driving their existing vehicles. Once anyone makes a large enough capital investment in anything there's pressure to keep it around and maintain it even though there may be something newer and better available. If that example seems silly, consider smart phones where over half of the country could afford upgrading every single year. Stuff that works tends to stick around even if it could be replaced.