Taking the weight off the crank is primarily to remove weight from the front of the car, not to reduce rotating inertia. My SCAT crank is 54 lbs which is 13 lbs lighter than a factory 383 crank. So that is 13 lbs off the nose of the car. My pistons and rods are also lighter than stock by roughly 1 lb each so that is another 8 lbs off the nose of the car.

It probably doesn't matter on a bracket car but on a competitive class car there is a huge advantage to taking 20 lbs off the nose of the car and putting it in the trunk.

You should see some of the circle track cranks, especially the sprint car stuff. They take a ton of weight off of those cranks, mostly to get the car as light as possible.