I've always thought of it as asking harder and harder questions until the junior person has to say "I don't know," as must happen eventually due to the seniority and experience of the questioner, setting up the victim to fail no matter how much they might be above their level of training. "See? I know more than you do, and don't you forget it. And I'm going to make you admit it in public, too." [and grovel in it...] It's really a form of bullying.

I always considered it revealed a character flaw in the questioner.