[DINKDINK]

>There's also a lot of resistance to electronic banking in... certain circles

In the USA as of 2017, 8.4 million households (6.5% of households) don't have any bank account. [1]

[1] https://www.fdic.gov/householdsurvey/

[perl4ever]

Undocumented immigrants are about 5% of the workforce, so that could account for most of them.