Why limit state method is most sue in compare of working stress method?

In limit state method, for each material and load, a partial safety factor is assigned individually depending on the material properties and load properties. Thus, each element of load and material properties is accurately assessed resulting in a more refined and accurate analysis of the structure. In this way, the material strength can be utilized to its maximum value during its lifespan and loads can be assessed with reasonable probability of occurrence. Limit state approach is commonly used for the majority of reinforced concrete design because it ensures the utilization of material strength with the lowest construction cost input.