Because interrogations are intended to coerce confessions, interrogators feel themselves justified in using their coercive means. Consistency regarding the technique is not important; inducing anxiety and fear is the point.
“Of all the toys available, none is better designed than the owner himself. A large multipurpose plaything, its parts can be made to move in almost any direction. It comes completely assembled, and it makes a sound when you jump on it.”
“It is only the farmer who faithfully plants seeds in the Spring, who reaps a harvest in the Autumn.”