Ever been to Chicago? There's a check-cashing shop (they call them "currency exchanges") on almost every block. If you are willing to pay whatever percentage they charge to cash your payroll check, you can get by without a bank account. WHY people do this I do not know, but large numbers do.

The last time I researched the issue the government quoted the national number at 20%. It skews higher for minorities and low-income people. You're welcome to your intuitions -- it might only be 40%. Either way, it isn't a small number or one which is evenly distributed across all demographics.