Why should all pilots use the local altimeter setting?

Using the local altimeter setting is crucial as it provides data for better vertical separation of aircraft. When all pilots use the same local altimeter setting, it ensures that altitude assignments are consistent across the airspace. This consistency is essential for maintaining safe vertical separation between aircraft, particularly in regions of high traffic or when flying in close proximity to other aircraft. By having a common reference point for altitude, the risk of altitude misjudgments is minimized, enhancing overall safety in the aviation system. This practice helps to prevent potential collisions and maintain an orderly flow of air traffic.