Because people/companies aren't the rational actors tradition economics makes them out to be. Case in point: low credit scores are uncorrelated or even positive

Because people/companies aren't the rational actors tradition economics makes them out to be. Case in point: low credit scores are uncorrelated or even positively correlated with good job performance (cf. the featured article's citations). Yet regardless, companies still base hiring decisions off of them (in the wrong direction, the data suggests). Mr Carpenter had to go through undue hardship due to ignorance and stereotyping of poor people. In summary, I hope Adam Smith's invisible hand slaps some sense into these companies.