Here's why:

* Newton: A newton is the standard unit of force in the International System of Units (SI). It is defined as the amount of force required to accelerate a 1 kilogram mass at 1 meter per second squared.

* Kilogram: A kilogram is the standard unit of mass. Mass is a measure of how much matter an object contains, while force is a push or pull that can cause a change in motion.

In summary: While kilograms are related to force through Newton's second law of motion (F = ma), they don't directly measure force.