The benefit was getting the GA organisations to agree with a mandatory transponder requirement for all E. The first such agreement I know of anywhere in the world.
I convinced the GA organisations including AOPA that to reduce the giant road blocks in the sky it would be worth agreeing to mandatory mode C even though there was no cost benefit study. In fact the FAA stated that they had no requirement for mandatory transponders in E over D because there was not a measurable safety problem.
Then AsA acted in a totally unethical way and removed the E but then insisted that CASA let the transponder mandate remain in all E and in non radar C- which previously did not have a transponder mandate.
Howabout most pilots I know including myself ,when flying VFR , take the extra distance and fly around non radar class C. Otherwise you get delayed and stuffed around as the poor procedural controller in a tower has to some how keep you separated . It is clearly a giant expensive road block in the sky.