I may be wrong on this but...my understanding it is to get even dampening left and right. With a single damper to get the same angle on the damper on both the left and right of the pod it would have to be attached to the center of the pod but that throws the weight off on the car unless you do something like what 3Racing did on their F109 which attaches the center of the damper to the center of the pod. If you attach a damper off-set to one side so that the damper can be centered then the arc in which the pod end of the damper moves is different from left to right. Using 2 damper tubes instead takes a lot of geometry out of trying to figure out where to mount the damper.