Here's why:
* Moment of inertia is a measure of an object's resistance to changes in its rotational motion. It depends on the object's mass distribution and the axis of rotation.
* Rotation is the actual movement of an object around an axis.
Think of it this way:
* A stationary car has a moment of inertia even though it's not moving. It's harder to get it moving (rotate) than a smaller, lighter car because it has more mass distributed further from its axis of rotation.
* Similarly, a spinning top at rest still has a moment of inertia. It takes effort to get it spinning in the first place.
In essence, moment of inertia is a property of an object, not a consequence of its motion. It exists whether the object is rotating or not.
