I can see the potential problems, but maybe a part of the solution would be to legally give the poor a right to a basic/free bank account.
The first thing that happens when they're in debt is that their bank account gets frozen to pay the debts leaving them with nothing.
Forcing all transactions to be electronic takes away the margins they live in. It's no longer possible for them to pay 1/2 their rent with a promise to pay the rest in a couple of days when they get paid so that they can feed their children during that period. The rent comes out of their account on time and their children go hungry until payday.
> It's no longer possible for them to pay 1/2 their rent with a promise to pay the rest in a couple of days when they get paid so that they can feed their children during that period.
Why not? You can transfer money whenever you want.