Here's why:

* Speed is a scalar quantity, meaning it only has magnitude (how fast an object is moving).

* Velocity is a vector quantity, meaning it has both magnitude and direction.

* Instantaneous velocity is the velocity of an object at a specific point in time.

Therefore, instantaneous speed is simply the absolute value (magnitude) of the instantaneous velocity. It tells you how fast the object is moving at that moment, without specifying the direction.