Why is this the answer?

The answer is spurs because this clever riddle uses fun word tricks to describe a special tool that people who ride horses wear. It is a mystery about something very familiar to a rider. Let's break down the first part of the riddle: "We travel much, yet prisoners are, and close confined to boot." This clue tells you exactly where the object lives. A spur is a small piece of metal that a rider fastens right onto the back heel of their riding boot. So, when the rider goes anywhere, the spurs travel "much" with them. They are like "prisoners" because they are stuck, or "confined," to that boot. They cannot go anywhere by themselves! They are locked in place on the foot, which is a clever way for the riddle to make you think of something being held captive. The next line talks about animals: "Yet with any horse, we will keep the pace." This is the big clue. People wear spurs to signal the horse to keep up or quicken its speed. The spur helps the rider tell the horse to move with a certain "pace," whether that means a fast gallop or a slow walk. The spurs keep moving right along with the horse and the rider, always staying at the correct speed. The final part is a great word puzzle: "and will always go on foot." This is a twist because even though the rider is sitting on the back of the horse, the spurs are never actually left behind. They are always fixed "on foot," since they are fastened onto the boot that is on the person's foot. The whole riddle describes the spur's life perfectly. It travels wherever the foot goes, it is a tool for horse riding, and it is a small, useful metal object that is always connected to the boot. This is a very old and smart riddle.