Re: "...It's fine for me but why would the stores trust these people to work for them when they are not qualified to run a cash register?"
Because it's cheaper for the employer to let you profit a few dollars because his affirmative action employee can't add or subtract, than it is for the employer to be sued by the Federal Equal Opportunity Commission for not having enough coloured people on the payroll; thus ending up paying a fine of $50,000.00 or even more.
As a matter of fact, the "affirmative action gestapo" of the Federal Government frequently puts many businesses permanently out of business with restrictions which can not be met, and with frivolous illegal lawsuits based on skin color quotas set by the Feds.
Compared to that, giving you enough money for a gallon of gasoline is a real bargain.