To limit the probability that excessive variance in the configuration of a flight of stairs will disrupt the gait of users or force them to switch to the other side of the stair, which could lead to difficulties in movement in an emergency situation, which could lead to delays in the evacuation or movement of persons to a safe place, which could lead to harm to persons.
To limit the probability that excessive variance in the configuration of a flight of stairs will disrupt the gait of users or force them to switch to the other side of the stair, which could lead to persons tripping or falling, which could lead to harm to persons.