I’m not really sure any of this actually explains a majority of the unbanked. Sure, it explains why people engaged in illicit trade don’t use a bank, but I find it hard to believe that is a sufficient explanation, especially when compared to lack of identification, perceptions of banks, and perhaps lack viable products (eg A checking account with “$25 maintenance fee waved if you keep a balance of $500 or more” is out of reach for the paycheck to paycheck crowd.)
Many illegal workers don't have accounts and either can't get them or don't trust banks.
Many of the poor get paid directly in cash for various reasons; you'd have to convince some of them that they need an account.
Then there's the whole criminal enterprise thing, a not inconsequential chunk of the economy.