Envelope combination not for design

Why is reinforcement design so robust when I define an envelope-type load combination?

Answer: An envelope-type load combination should not be defined for design because ETABS, SAFE, and SAP2000 consider each load combination separately, generate a design for each load combination, then envelope this resultant set of design specifications to provide maximum positive and negative reinforcement. When an envelope combination is defined manually, the maximum moment, shear, axial, and torsional response from all load combinations are superimposed on a single design process which generates an over-designed system with capacity for unrealistically extreme loading.