Like any bureaucracy, the ATF has to justify its existence. Enforcing alcohol and tobacco laws is pretty far down the line of law enforcement prestige and is decidedly "non-sexy." If enforcement of firearms law was moved to the FBI or other legitimate law enforcement agency (Secret Service?), there would be less pressure for the agency to prove itself and justify its existence through bogus and ill-conceived efforts to ring up numbers and arrests or be a willing political tool. The law enforcement agency assuming the responsibilities would have other duties and responsibilities to help justify its existence. There would consequently be less motive to engage in unlawful behavior.
Jim's Rules of Carry: 1. Any gun is better than no gun. 2. A gun that is reliable is better than a gun that is not. 3. A hole in the right place is better than a hole in the wrong place. 4. A bigger hole is a better hole.