Because it is the institutional mindset of the TSA that it is accountable to nobody. That mindset is evident from Stone on down throughout management.

At some point (BOS for example), the front-line screeners develop the same mindset/attitude of non-accountability as the management.

The open bag is yet another example of either laziness or incompetence. Given the billions of dollars that the TSA wastes and the "Professionalism" we were promised by Tom Daschle when he created this joke of an agency, neither is acceptable.