I see no problem at all.
1. Fiat currency will not die off, so these people don't have to use Bitcoin if they don't want to.
2. Even
some of the stone age people can use bank cards (debit, credit). Bitcoin use
will become this easy sooner or later.
What i can see is that most of such kind of peoples don't even knew to use credit/debit cards and had rarely any bank accounts. So did it really quit banks?

No, but it made them to go for it and atleast learn some basic transactions. The same will go ahead with bitcoins too.
Understanding bitcoins is not that complex and if peoples can learn using debit/credit cards, they should also start learning bitcoin transactions. A good alternative for it would be launching bitcoin ATM's globally with bitcoin debit cards. This is really going to make Bitcoin transactions much easier than we ever thought.