That needs a lot of bureaucracy involved, and leaves a paper trail that could interfere with later political prosecutions built on parallel construction. If a person, "willingly," let's them in, they can avoid all that, and usually keep the spying for probably cause, or planting of digital evidence (or real evidence, using the online info to figure out how to do it sneakily), hidden from the defense.
So the feds aren't capable of running their own, faster exit node? Like host it in Room 641A?
Clearly it's just more fun for them to ruin some dude's life and leave the perceived problem unresolved to get another budget bump.
That needs a lot of bureaucracy involved, and leaves a paper trail that could interfere with later political prosecutions built on parallel construction. If a person, "willingly," let's them in, they can avoid all that, and usually keep the spying for probably cause, or planting of digital evidence (or real evidence, using the online info to figure out how to do it sneakily), hidden from the defense.