US Treasury is Missing 21 Trillion Dollars

At first it seems like this is an indictment of the Treasury for failing to properly audit their complex accounting. These two savvy people present the situation just that way. They also inform us of the Internal Revenue "Service" determination to pursue 7 trillion of their losses as new taxation. But, in this climate of translucent corruption, where no one even makes much of an attempt to hide their theft, why do we focus on "incompetence" when it is much more likely that the ruling class have been tapping the bladder of the money cow for decades?