Why is there always uncertainty in every measurement?

Uncertainty in measurements arises from various factors, including limitations in the measuring instrument's precision, environmental influences, and the inherent variability of the quantity being measured. No instrument can measure a value with absolute perfection, as there are always small errors or fluctuations that can affect the result. Additionally, human factors, such as reading errors or subjective interpretation, can introduce further uncertainty. Thus, every measurement is an approximation rather than an exact value.