I've made a research about this before, and as far as I remember, most reasons why people in the rural area stays unbanked is because usually banks are far from their area which make it unaccessible to most of them, the lack of funds to have an access to financial services, and no proper financial education. Bitcoin may help in solving some problems such as ccessibility, but it will still depends if they have access to internet connection in their area. Bitcoin is also cheaper when it comes to transaction costs, also it doesn't need any maintaining balance unlike with banks.  However, if a lot of people not just in rural area, still lack in basic financial education, it may be hard for them to adapt Bitcoin since it can be too complicated for them.
Bitcoin can solve some problems why people are still unbanked, but only to few. It's not an institution that provides various financial services to everyone.