From a USA Today article in 2010: Nearly 8% of U.S. households, or about 17 million people, don't have bank accounts, according to a 2009 study by the Federal Deposit Insurance Corp. An additional 18% 43 million people are "underbanked," which means they have bank accounts but occasionally use check-cashing companies, pawn shops, liquor stores or other alternatives to cash checks, pay bills and borrow money. African Americans and Hispanics are much more likely to be unbanked or underbanked than whites, the report found.
That's why Walmart does such a big business of cashing checks for people. It's hard where I live to do a return at Walmart because there is always a line of people buying money orders, cashing paychecks and doing western union transfers at the service desk.