Entertaining, because there are hella hot girls, and it's interesting psychologically because you wonder what you would do if you were in the same situation. They are not diametrically opposed.
Nice people are boring.
Sorry, it's true. I personally wouldn't do it, but if they want to do it, it's their call. It seems unrealistic and cheesy. You find out if the couples are actually truthful to each other and how strong their relationship is. It's an obstacle course for a relationship, and it's fun to watch because it's not me.