Before revision: The reason for the disparity between factors for dead load and live load, and thus the reason the loads are initially categorized as dead or live is because while it is not unreasonable to expect a large number of people ascending the staircase at once, it is less likely that the structure will experience much change in its permanent load size of the load factor is based on the probability of exceeding any specified design load.
After revision: The size of the load factor is based on the probability of exceeding any specified design load.