In interrogation, even lies matter to a trained interrogator. He knows that the prisoner will try to lie, but He keeps on asking the same questions over and over, sometimes with a twist, and eventually the prisoner trips himself up or lets something useful slip.
And then there are the tidbits of good info that operatives are trained to give up, albeit slowly.
And there are people who haven’t been trained to withstand the technique and give up everything they know immediately.
And be used for propaganda purposes. . .like the Navy guys captured by the Iranians.