Maybe I’m a bit slow, but I understood why there will be no rewards for cascades in Treasure Hunt just yesterday. A usual battle is about removing gems/skulls from the board by matching 3, 4 or 5. But in TH it’s all about accumulating: treasures matched become another treasure of 1 level higher. So if you have a lucky cascade, you collect more treasures, i.e. it’s a self-rewarding process. (Even with kind of a penalty: we get no extra turns for additional 5 matches during cascades.)