Why is the proximate analysis of carbohydrate (nitrogen free extract) determined by difference instead of direct analysis?

Proximate analysis determines the major components of a food sample such as moisture, protein, fat, and ash. Carbohydrate content (nitrogen free extract) is calculated by difference because it encompasses all non-protein, non-fat, and non-ash components. This indirect approach accounts for any discrepancies or impurities in the sample, providing a more accurate estimation of the carbohydrate content.