Why is the settling time not visible on the step response diagram?

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The settling time is not explicitly visible on the step response diagram because it is a measure of how long it takes for the system to settle within a certain tolerance band around the final value. Therefore, it is more of a quantitative measure that cannot be easily represented visually on the step response diagram. However, the step response diagram does give an indication of how quickly the system reaches its steady-state value, which is related to the settling time.