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.
“I was playing rugby and the other games English school children do, and there was an event in which races were run, and I won these by a considerable margin.”
“I always felt like my future was at stake every time I stepped on stage and that was kind of hair-raising. At some point I just went, don't be frightened, you can't do anything wrong, it's your show.”