Here is the thing you have to remember. ATF was originally justified as a Federal Agency on the premise of it doing national level crime fighting across state lines (affecting interstate commerce). If anyone ever looked closely at the statistics, the vast majority of cases are simply adopted from the local PD or are local nickle and dime thugs with no real federal interest. Other than doing a nexus statement saying "this gun traveled across a state line sometime in its live" ATF serves no real national mission any longer. You could hire 2-3 local cops for the cost of one agent and impact crime more. Even on those occasions when a "big" case is attempted, there are so many fingers in the pie with incompetent supervisors clamoring for a pat on the head, that it can't help but get fucked up and no one goes to jail.
When you have a national attention shooting ATF shows up to simply show the jackets for the press. At the most, they take the serial number of the gun and do a trace for the FBI or local LE to where it was purchased....which a high school kid could do. If the world knew that the average agent makes $120K to do only a couple of simple cases a year or none at all (PA0/Project Officers/Program Managers/Dog Handles, Tech, Intel, etc)......and the useless supervisors are making upwards of $150k to poorly duplicate what the local cops are doing, there might be some blow back. Think about a young sergeant in Afghanistan and the responsibility he has for his troops.....which are significantly more than 10. The sergeant makes no where near $150K for actually doing something dangerous. An ATF RAC crys about how hard it is to run an office of maybe 10 (tops) and pulls $150K to sit behind a desk reading reports, going to the gym and home in his government provided car at 4:00
So, do you still wonder why they cook the books any which way they can on the statistics?