To make it easy to check for rouge or organized terrorists, is to make the country ripe for attack from large countries.
We assume that our enemy will be terrorists, but that may not me. Out next enemy may be another country. In that case you want all of your web of contractors, which is inclusive of so much more than just the primary contractor, you want them all secure.
Have you heard of: "loose lips sink ships?"
Our nation needs to be secure even at times from itself.