And, as with all of the supernatural "woo" shows, they have to find a way to keep interest and a story going in the absence of any resolution, ever. Anything called "Finding Bigfoot" has to deal with the fact that they will never find Bigfoot, any show called "In Search of Ancient Aliens" will never dig any up, and "Secrets of Skinwalker Ranch" will never be able to reveal any secrets. (Assume for a moment that there was a Bigfoot to find, and that the "Finding Bigfoot" cast and crew found it -- this news would come out LONG before the series finale of the show! If you have not already seen massive news coverage of the discovery, you can know they are not going to find ol' Sasquatch !)
These shows sell the sizzle, but will never provide the steak, there will never be any substance to them. (Treasure hunting shows might have an advantage here -- the specific treasure they are looking for may not exist, but treasures do get found from time to time, so it is not impossible they'll find one.) It is not surprising that an audience would watch a show for a time just for the sizzle, but it is still surprising to me that these shows can run season after season with nothing to ever show for it, and people keep coming back.