Here's why:

* Circular motion requires a change in direction: Even if an object moves at a constant speed in a circle, its velocity is constantly changing because its direction is changing.

* Acceleration is a change in velocity: Since velocity includes both speed and direction, a change in direction means a change in velocity, which means there's acceleration.

* Centripetal acceleration points towards the center: This acceleration is always directed towards the center of the circle, constantly pulling the object inwards, preventing it from moving in a straight line and causing it to follow the circular path.

Important Note: While centripetal acceleration is present in circular motion, tangential acceleration can also be present. Tangential acceleration changes the *speed* of the object in circular motion. If the speed is constant, there is no tangential acceleration.