I believe, there are 2 reasons for that: 1) there are some problems in Africa that can be solved with Bitcoin, such as remittances 2) MMM, obviously 

And it also allows many Africans to make money, you know. If they are able to buy Bitcoins on exchanges, they can later sell them to other people at a higher exchange rate for ZAR.

Makes sense they google about that and create websites on where to buy Bitcoins, such as this one.

So, everyone tries to do business in this world

Yes, that makes sense. I keep my money in different places even when I travel somewhere. So, if I lose a card, I still have cash and vice versa.

Of course, you do not want to get any satoshi lost, but still... better to lose a tiny bit, than everything.

Well, I think that loading Bitcoins to an exchange is similar to opening a deposit at your bank. There is no 100% guarantee, but you still have criteria to choose the best and trustworthy exchange or bank. If you don't want to do that, keep your money/Bitcoins under your bed/in your wallets.
I mostly keep BTC on my wallet, and trade the rest of them on CEX.IO. I chose them, because they've been on the market for a long time, have registration docs right on the website, PCI DSS certificate, have cold wallets, and all the stuff. And they suit me in terms of easy deposits and withdrawals using credit cards, which is very important for me.

mobile app, first and foremost

The article headline is very negative biased. In the article itself it discusses the ability to trade the GHS and that is an advantage CEX has over other cloud miners. Just sitting on cloud hashing won't yield a decent enough profit regardless of wjo the provider is, same as just sitting on cash in the bank won't. I've only just tried it out myself, but can see how the mining and trading combnination works very well. .https://bitcointalk.org/index.php?topic=317001.msg6726473#msg6726473