There are too many people outside of the US Government who have access to Top Secret and above classified information. There is little allegiance to employers and our national security is at risk, evidenced by what happened with Booz Allen Hamilton. Federal employees are vetted by the US Government and not by an private firm, whose only allegiance is to making a profit, which endangers the entire country by hiring sub-par employees.
In addition, we are paying private contractors significantly more than a government employee would make. This would reduce spending as well as making our nation safer.