3rd time that type of explanation has been offered. The factory setup pressures on the cam are not nearly as high as what they can be for performance cams. Those pressures come not just from springs but from acceleration of the big mass of the roller lifters up faster and faster ramp cams at higher and higher RPM's. At some point, the inexpensive, cast factory cam material can't take the increased pressures, and the cam material fails, so the material change is mandatory.
