Searches and scannings are not designed to catch terrorists or wrongdoers. Many people within the police, TSA, border control, NSA and Department of Defense have confirmed that nearly all anti-terrorist measures have not yielded any results in effectively stopping terrorists. And yet somehow, there are almost never any terrorists attacks in North America.
The truth is that there is no "terrorist threat" and that these "security measures" are all part of a fear-mongering propaganda to convince the American public that it is acceptable to maintain an insanely powerful and out-of-proportion military presence abroad.
Just look at the latest scandal in security. The NSA has been tapping phone calls and copying emails of countless millions, both inside the US and outside. Private individuals and public officials. And yet the NSA has reported that "at most one terror attack might have been prevented". Might have been.