Why is this the answer?

The answer is water because this fantastic riddle gives us two perfect clues that describe exactly how water moves in the world. Let us look at the first line: "Runs smoother than any rhyme." Think about when you watch a little stream running over rocks or when you pour a glass of water at the dinner table. When you see water move, it is always flowing in a beautiful, calm, and continuous way. It never stops or stutters unless something solid blocks its path. It can fill any shape, slide right past any corner, and always follow the easiest path it can find. The way it moves is so easy and graceful, like a perfect song or poem that is all about flowing from one note to the next. The water seems to just glide along the ground, much smoother than anything else you can imagine. A rhyme is often very steady and smooth, and water is even smoother than the best poem. This is why sailors and poets often write about the calm, flowing nature of water in a stream or on the ocean tide. Now let us look at the second, very important clue: "loves to fall but cannot climb!" This clue is all about the way water must move because of the world's most powerful rule: gravity. Have you ever seen a huge waterfall or a river rushing quickly toward the sea? It is the best example of this riddle. Water loves to fall down because gravity is the invisible force that pulls everything down to the ground, including the water. That is why when you drop a ball, it falls, and it is why water in a river always rushes toward a lower spot, like going down a hill. Even if it is in tiny drops of rain, it still falls from the sky. Water can go down a mountain and fill up a lake, but it can never climb back up the mountain by itself. It can be carried up in a bucket or pumped up with a machine, but the water itself will always follow the path that takes it down. This simple, clear liquid is always obeying the rule of falling, and that is why the clever answer to the riddle is water.