Why would a hand held stopwatch NOT accurate times for a race?

A handheld stopwatch may not provide accurate timing for a race due to human error in starting and stopping the timer, leading to delays or premature stops. Additionally, the reaction time of the person operating the stopwatch can introduce inconsistencies, especially in races with precise time requirements. Environmental factors, such as distractions or the operator's focus, can also affect timing accuracy. Lastly, the stopwatch may have limitations in resolution, preventing it from capturing very precise times needed for competitive events.