318 head porting for the average joe

question: If the short side radius and valve blend is so easy to do , why did Mopar not cast this into the heads from day one? C'mon, you cant tell me in the HP race of the late 60's that Chrysler didnt see this garbage as low hanging fruit for an easy casting fix? Its funny to see basic porting add 50HP and not have it realized by Mopar. Do these porting steps kill real world street RPM torque?