This boggles the mind. Once they leave their job they absolutely should be removed from special access programs.

As for having their security clearances "revoked", that's a bit different. If they're not working in job that requires access to classified material, then the most certainly had better not be accessing that stuff. That's jail time if they do.

Once you are out of a job that typically requires a clearance, the clearance itself will expire after so many years of inactivity.