Why is this the answer?

The answer is rope because this clever riddle uses fun word pictures to describe an object you see all the time. Imagine a long piece of rope. When it is not being used, it is often wound up, or "coiled," into a big, neat, round circle on the floor, just like the first line says: "Snake coiled round and round." It looks like a very big, sleeping snake waiting for its job. The second line gives you an even better clue when it says, "Snake that's never had a head." We know a rope is not a real animal. It is a very long, strong piece of fiber twisted together. It might look like a snake when it is coiled, but it has no head, no eyes, and cannot wiggle on its own. This clue helps us understand that we are looking for an object that is only shaped like a snake, not a living creature. The third line, "Snake deep below the ground," is a bit of a trick. Ropes can be used for many things, and sometimes that means going down low. Think about a farmer dropping a bucket deep into a well to get water. They use a rope to do that! Or, imagine a ship dropping an anchor into the ocean to hold it in place. The anchor is attached to a rope, and the anchor goes deep down to the bottom. So the rope is often "deep below the ground" or the surface of the water, which is a neat way to describe its important work. Finally, the last clue says, "Snake that binds but not with dread." To "bind" means to tie something up, which is a rope's most important job. It ties up big packages, binds logs together, or ties a boat safely to the dock. The riddle says "not with dread" because even though you are tying something, it is usually for a good and helpful reason, not a scary one. A rope is simply a very useful tool! Every line of the riddle helps paint a picture of a helpful, long, coiling rope.