There was a time when I was flagged for pre-boarding check on nearly every international flight into the US. But then upon arrival I would spend 5 minutes being questioned at the CBP booth and sometimes even be sent to secondary.

But if you have the capabilities to flag me pre-flight, why do I need to get checked again after landing? I doubt that this was unique to me and more frequent travelers had this happen. The costs to do it like this must be immense, and it was all wasted effort on someone that was literally providing employment for US citizens.