"The investigations are what keep the agents’ minds sharp, which reinforces their effectiveness on protective details. The best protective agents are often the smartest ones, because they know how to read people. That comes from investigations.” It may be true that if you designed the entire national-security apparatus from scratch, investigating financial crimes would fall outside the purview of the Secret Service. But from the agency’s point of view, its hybrid nature is a feature, not a bug."
Inside the Secret Service