There's a reason for this. The reason lies at the heart of law enforcement methodology in general and federal law enforcement abuse of Title 18, United States Code, Section 1001 in particular.
Imagine this scenario, based on an actual situation:
A business associate calls you and says, "my dear business associate, the shit has hit the fan; Federal Agency X is investigating Project Y we did together. Two Agency X agents are interviewing people."
"Oh coitus," says you, or words to that effect, and terminate the conversation.
Later that day, two well-dressed and polite agents of Agency X visit you. Because you despise me and want me to weep and gnash my teeth, you consent to be interviewed. At some point, they ask you "have you talked about this investigation with anyone?"
"No," you say.
At the end of the interview, it occurs to you to ask, "Hey, am I in trouble? Do I need a lawyer?"
The agents smirk. "No," they say. "I mean, unless you lied about talking to anyone about this investigation."
See, you've fallen into a false statement trap, which I've talked about before. The feds know that you've talked to somebody about their investigation. They were probably standing next to your friend when he made that call this morning. And now you've talked your way into a felony.
Here's how it works. The feds identify some fact that they can prove. It need not be inherently incriminating; it might be whether you were at a particular meeting, or whether you talked to someone about the existence of the investigation. They determine that they have irrefutable proof of this fact. Then, when they interview you, they ask you a question about the fact, hoping that you will lie. Often they employ professional questioning tactics to make it more likely you will lie — for instance, by phrasing the question or employing a tone of voice to make the fact sound sinister. You — having already been foolhardy enough to talk to them without a lawyer — obligingly lie about this fact. Then, even though there was never any question about the fact, even though your lie did not deter the federal government for a microsecond, they have you nailed for a false statement to a government agent in violation of 18 USC 1001. To be a crime under Section 1001, a statement must be material — but the federal courts have generally supported the government's position that the question is not whether a false statement actually did influence the government, but whether it was the sort of false statement that could have influenced the government.
Hence, the government's chickenshit false statement trap works — even though the government agents set it up from the start. Now, however weak or strong their evidence is of the issue they are investigating, they've got you on a Section 1001 charge — a federal felony. In effect, they are manufacturing felonies in the course of investigations.
You think this is an improbable scenario? You think I'm talking about rare and extreme cases to color the entirety of federal law enforcement? To the contrary, as a federal defense attorney, I'm encountering this more and more often. Not to sound like an old fart, but we never indulged in such bullshit when I was a federal prosecutor (cue the scoffing from many defense attorneys). But in the last 12 years, I've seen it in a dozen cases, and heard about it from colleagues across the country. It's now routine for federal agents to close out an investigation with a false-statement-trap interview of a target in an effort to add a Section 1001 cherry to the top of the cake.
The lesson — other than that criminal justice often has little to do with actual justice — is this: for God's sake shut up. Law enforcement agents seeking to interview you are not your friends. You cannot count on "just clearing this one thing up." Demand to talk to a lawyer before talking to the cops. Every time.