To make sense of this puzzle, I read a variety of interesting histories. The most interesting source was “The Leaky Leviathan,” by David E. Pozen of Columbia Law School.
Pozen stresses that leaks serve the purpose of the federal government more often than not. A survey from the mid-1980s found that 42 percent of surveyed senior government officials felt that it was sometimes appropriate to leak information to the press -- hardly a sign this is intrinsically treasonous behavior. ...
Sometimes governments trade leaked information to reporters, to curry favor. Other times leaks are used to hurt rivals within the public sphere, or a leak can serve as a trial balloon to test the popularity of an idea. Leaks also may help a president’s Cabinet members build up their own internal empires, which can boost a president’s agenda.
Or the American government may want to inform its people about, say, drone operations in Yemen, but without having to answer questions about the details. In this regard, leaks may substitute for more direct congressional oversight, to the benefit of the executive.
In other words, leaks are part of how the government manages the press and maintains its own popularity. ...
Leaks are also a way of threatening other governments, yet without the president putting all of his credibility on the line. For instance, it can be leaked that the national security establishment would be especially unhappy with a further expansion of Israeli West Bank settlements. That sends a message, yet without committing the American government to any particular response if the settlements proceed. Or leaks can signal to foreign terrorists or governments that we know what they are up to.
Of course, many leaks are unwelcome, such as when national security confidences are disclosed. Given that reality, why haven’t American governments worked harder to prosecute unwelcome leaks and leakers?
Well, if that policy were pursued successfully, the only leaks that would occur would be “approved” or government-intended leaks, and everyone would figure this out. The government could no longer use leaks as a way of providing information or making threats in a distanced manner with plausible deniability.
--Tyler Cowen, BloombergView, on solving for the equilibrium