In Cameroon, where cash is still widely used, there's a serious shortage in coins, and it's been the case for my whole life (I'm not that young anymore!).
With a 10k cfa note (~16 usd), or even a 5k note, you run the danger of not being able to use it, because merchants very often don't have change. 
Ironically, despite this major issue, mobile money acceptance was very low for a very long time, initially because it was new tech and people had trust issues, but it is getting better...