Why is angular momentum conserved during a collision, while linear momentum is not conserved?

Angular momentum is conserved during a collision because the total amount of rotational motion remains constant due to the principle of conservation of angular momentum. This is because there are no external torques acting on the system during the collision. On the other hand, linear momentum is not conserved during a collision because external forces, such as friction or air resistance, can act on the objects involved, causing a change in their linear motion.