You have to view this from TSA's side.
They are part of a group of people of which most have nothing to do. Even the lowest forms of life can remain idle for so long and then have to move. This requires they look busy in order to keep their job.

Trying to look busy results in;
Searching for items other than Aviation Threats.
Gate Searches.
Wandering the Concourses.
Running useless Drills, and Proceedures.
Secondary Screening.
and the list goes on & on.