Bronze gear necessary??

I guess my point is why don't they make the roller cams out of the same material the factory roller cams are made out of and then we can just use our factory gear drives/shaft like we've been doing for 60 years with all the LA's?
Because of the higher pressures/lobe profile and hardened wheels. You can use cast iron core like a factory cam, but the wear will be much greater in a performance race app.