To discourage applicants with something to hide. In this case, just having a pre-screening job program discourages job applicants with a criminal background or falsified credentials. To eliminate uncertainty in the hiring process. Many employers have learned the hard way that relying on instinct alone is not enough. To demonstrate Due Diligence.
Many employers have a reasonable duty of care in the hiring process.
To not only discourage the wrong kind of applicant, but encourage the right applicant to be open and truthful. This introduces honesty into the application and interview process. Employers' find that just having a background program will encourage application to be more forthcoming about their history. The companies we spoke with all provide substantial resources to those staffing companies that wish to implement a screening program. For the great majority of companies that do not work with the government, Due Diligence is the most applicable regulation.