Here's why:

* Newton (N) is the unit of force in the International System of Units (SI).

* Newtonmeter (Nm) is the unit of torque, which is a rotational force. While torque is related to force, it's not the same thing.

To clarify:

* If you want to measure force directly, you would use a force gauge or dynamometer, which will give you a reading in Newtons.

* If you want to measure torque, you would use a torque wrench, which will give you a reading in Newtonmeters.