Here's why:

* Electromagnetic waves are disturbances in electric and magnetic fields that propagate through space at the speed of light. They do not require a medium to travel, unlike mechanical waves.

* Mechanical waves require a medium to travel. This medium is composed of particles that vibrate and transfer energy. Examples of mechanical waves include sound waves and water waves.

Light waves consist of oscillating electric and magnetic fields that are perpendicular to each other and to the direction of wave propagation. They can travel through a vacuum (like space), which means they don't need a medium.