Here's why:

* Breakdown: The small intestine is where most of the digestion of carbohydrates, proteins, and fats is completed.

* Absorption: The small intestine has a large surface area due to its folds, villi, and microvilli. This allows for efficient absorption of the broken-down food molecules into the bloodstream.

* Capillaries: The small intestine is heavily vascularized with blood capillaries that run close to the absorptive surface. These capillaries pick up the absorbed nutrients and transport them to the rest of the body.

While some absorption happens in the stomach, the small intestine is the primary site for assimilation of food molecules into the bloodstream.