Can you explain to me why the polygraph IS reliable to detect lies?

I know most research tells you no, but they have used it in a game show, “The moment of Truth”, to win $500,000, and, though without a doubt being sued, to my knowledge a guilty verdict must still be issued. They even released the episodes on YouTube. So, I’d like for you, as a personal favor, to play devil’s advocate and tell me why the lie detector has some practical effect (other than to scare people, I mean). For the record, the lie detector can also give inconclusive results. And, in the game show, they ask with the polygraph 50 questions circa, then they select 15 for the contestant, and they process the answers to the questions through the polygraph again. (S)he must ALWAYS tell the truth. The guests on the program (parents, friends, etc.) can stop the questions ONCE, but they have NOT idea if the next question is more difficult or easier. Last thing: 2 seasons, only 1 contestant won $500,000 but their complete attendance was NOT recorded on YouTube.