Most of their population don't have access to bank accounts, and bitcoin can help here. Their coins are usually poor, and have no economic power
They don't have access to bank accounts, how do you expect these people to use bitcoin when they get to know on how banks work,crypto will be too much for them, for, one at least 25% of the population in Africa are illiterate ; two, they don't have adequate facilities (some don't even have basic needs and necessities); three, the markets of crypto are too volatile for them to handle and all these will affect the people tremendously.
They don.t have access on bank accounts and you say they will download/install bitcoin core, save keys, buy trezor and etc..... They don't have computers and how will they have bank accounts? And who needs this accounts if they are very poor, don't have normal schools, don't learn and don't have ability to go in University, most of them even don't have basic things, it's easy to say for you because you don't know their poverty. No one cares about them and that's sad fact.