This is a very thoughtful and educative post. As you mentioned, I also don't know how widespread this practice is beyond the shores of Nigeria. Most people patronize this business because of a lack of power supply or inability to purchase electrical appliances.
To add to the solution, there are manual grinders as options too though a bit more tedious. Maybe substituting the components of the grinders during production can help🤷♀️. I'm not sure about the technicalities involved in that.
Incredible post!