Why is this the answer?

The answer is snail because this clever riddle uses fun word pictures to describe this slow moving garden friend and its little house. Let us look at the clues like we are detectives solving a case and breaking a secret code. The very first clue is "If a man carried my burden, he would break his back." This is the sneakiest part of the riddle. A snail’s "burden" is the hard, spiraled shell it carries all the time. That shell is the snail’s special home, and it has to carry it everywhere it goes to stay safe from danger. For the tiny snail, its shell is a big, heavy weight, but for a person, it is very light. The riddle is playing a wonderful trick on your mind because it makes you picture a strong man struggling. A man would not break his back because the shell is heavy, but because the idea of a grown-up trying to carry such a tiny, slimy shell as his own "burden" is a silly thought that might make him break down laughing. The shell is the snail's entire world, and a man cannot carry it in the same important way a snail does. Next, the riddle says, "I am not rich, but leave silver in my track." We know that a snail does not have a job and does not carry money, so it is not rich. However, when a snail moves slowly across the ground, it leaves behind a long, wet, and slippery trail. This trail is made of a special substance called mucus or slime. It helps the snail glide easily over all the rough rocks and dry dirt without getting hurt. When the sun shines on this damp, sticky track, it catches the light just right, making it sparkle and shimmer. It looks exactly like a tiny line of silver, like a secret, valuable path left behind on the grass. The snail does not need money to make its beautiful, silvery track. These two perfect clues, the house on its back and the sparkly silver trail, prove the answer is a snail.