It seems like crypto’s immediate use case for the developing world is as a store of value and a means for moving money internationally. I remember visiting countries like Kyrgyzstan and Cambodia and realizing that many people keep their life savings in USD cash hidden in their homes. When the banking system isn’t trusted, a crypto wallet could be seen as a viable alternative.
The main problem with bitcoin as a currency, aside from price volatility, is transaction time. Consider that it takes, on average, 10 minutes to mine a single bitcoin block capable of containing, at maximum, 3,500 transactions. Compare that to the 1,700 transactions processed by Visa every second. Unless some major change is implemented in bitcoin’s protocol, it’s hard to see how that system could scale to tens of millions, let alone billions, of daily payments.