About this question, some anglers said no, they do not need a tippet to fly fish. They thought like this... they don't have to worry so much like fishers about presentation as the dry fly. Since most of the flies, they are using streamers and nymphs.
But they forget that always they are using the leader with the fishing hook. Frequently, fly fishing with it damaged your expensive leader. On the other hand, tapered also made by monofilament nylon. Which is invisible in the water so, fishes only see the fly in the water and try to make it their food, they don't think it's a trapped indeed. These are the plus point to using a monofilament tippet to fly fish.