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.
I think you are missing the point. I "know" what kind of poverty you are talking about. Not by experience, but from the information we can get from the social media. Of course that if basic needs like water, food, and a place to live are lacking, those need to be addressed first. You can only start to build an economy once basic needs are addressed. But there are some countries where those needs are "functional", and there is room to try to develop education, economy and commerce.
It's also very common in those places, for people to leave their countries in order to find work and a way to support their family that stays behind. They usually face huge problems when it comes to send money back to their families. Specially when there are no banks around. As you may agree, it's a lot easier and cheaper to develop a telecom network, than it is to develop a bank network (banks actually need that first, so they can work properly). And this is where crypto may help. This is the kind of still very poor countries, where cryptocurrencies can help boost their economy, an Africa has a lot of these countries.