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.
“There are really only two plays: Romeo and Juliet, and put the darn ball in the basket.”
“At the moment, in Britain we're facing such enormous cutbacks in education programs and music programs and art programs that you feel you are knocking your head against a brick wall.”