Unfortunately, they have not been proven useful. The credit reporting agencies do sell it to companies as "useful" to measure a candidate's integrity and ability to succeed. However, if you watch John Oliver's segment you will see at least 1 agency testified under oath that they have no evidence to back up their claims.

All it can be said to do is to weed out poor people or conversely allow terrible employers to pinpoint candidates that they can easily abuse because they are so far in debt.