One word: Ratings. Well that, and I imagine “Nessie” gets tourism around the Loch Ness area. They probably sell fun stuff-like stuffed Nessies, and goofy teeshirts, maybe? (I used to be a Nessie fan when I was a kid). So maybe it goes hand in hand?
Do they still do History’s Mysteries, or History’s Crimes and Trials? Those two were my favorite.