Why convert Hawkins to six-inch guns

Why was a Hawkins-class cruiser considered for conversion to a six-inch light cruiser?

To eliminate the 7.5-inch logistics chain while fitting perhaps eight or ten standardized six-inch guns.

Removing the 7.5-inch battery would eliminate a specialized ammunition and support burden. Four or five twin six-inch turrets could also increase the number of guns, giving the rebuilt cruiser both simpler logistics and a heavier volume of fire.