Mechanical digestion, the process of breaking down large chunks of food into smaller pieces, is important because smaller pieces of food

The answer is Have a large surface area on which chemical enzymes in the digestive system can act on it. This increases the rate of digestion and absorption of the nutrients. The smaller an object is, the larger the surface area to volume ration it has compared to relatively larger objects.

Mechanical digestion, the process of breaking down large chunks of food into smaller pieces, is important pieces of food are more readily digested through chemical digestion.
The mechanical digestion begins with chewing. The action of chewing mechanically breaks down very large aggregates of food molecules into smaller particles. This results in the food having increased surface area, as important contributing factor to good digestion.