Why is this the answer?

The answer is age because this is a very clever riddle that plays a wonderful trick with words. When you first hear the question "What goes up but never comes down?" your brain probably pictures something you can physically see and touch. You might think of a hot air balloon floating into the sky, a baseball soaring after a strong hit, or maybe even an elevator climbing to the top of a tall building. But every one of those things that goes up in the air will always eventually come back down to the ground. That is the first part of the riddle’s secret, it tricks you into thinking about objects that move up and down. The correct answer, age, is not a physical object at all. Instead, it is a way to measure the time you have been alive. Imagine the numbers representing your age are like steps on a staircase. When you were born, you started on step zero. On your first birthday, you moved up to step one. Every single year on your birthday, you climb one more step up the staircase. This climb never reverses. Once you turn eight years old, you will never go back to being seven years old again. It is impossible to turn back the clock and become younger. Your age is always increasing, always going higher, year after year, forever moving forward with time. It is a one-way trip! The number representing how old you are only moves in one direction: it "goes up" and never, ever "comes down." This is what makes "age" the perfect and most accurate solution to this classic and tricky puzzle.