At some point organizations exist for the benefit of the organization only. What would success look like for people at DEA/ATF/etc?

The only true business value is trying to put oneself out of business.

What can the DEA do to prosecute more internally and externally? We would have to revert back to the ways of less human-rights friendly warfare. We would have to build physical and surveillance barriers. On borders. We would have to more heavily control shipments of goods and overall freedom of navigation of waters. We would have to turn our nation into a prison-island.

As for the ATF, well, only so much one can do for stolen arms… and even then we may have a critical mass problem. Unless we abolish the right to self-defense and start violating civil rights to clear the possession of weapons.

All politically untenable, and so what would rolling up these departments do other than consolidating power? They would have the exact same set of issues.

Much like invading Afghanistan, it’s a winnable issue in theory. After all, Alexander the Great did. However, modern political reality defeats you before the boardgame is out of the box.

Same as every other specialty law enforcement agency (campus police, transit system police, etc), prioritizing stuff that the "real police" would get raked over the coals for wasting resources on. You couldn't have the FBI kicking down the doors of medium time drug dealers and suburban dads who violated some arcane statute the way the DEA and ATF do in the same way that a city police department can't justify pissing away man-hours chasing every bum that Karen calls in for pissing on the train tracks. Easier to just spend the money on a bespoke enforcement agency than to have the hard conversations about political will and how much the long tail of stuff these organizations do actually matters.