Here's why:
* Smooth muscle is involuntary muscle, meaning it contracts without conscious control. This is essential for the rhythmic contractions, known as peristalsis, that push food along the digestive tract.
* Skeletal muscle is voluntary and attached to bones, allowing for conscious movement, not the squeezing action needed for digestion.
* Cardiac muscle is found only in the heart and is responsible for pumping blood.
So, smooth muscle is the key player in moving food through the digestive system.