Just guessing, but the short pumps were around for a long time. Then cars started getting longer. I suspect it was cheaper to make a longer water pump and change the pulley system than move the engine in an existing chassis.
They used several different balancers- there was a 6 that had a ring that was 3/4 wide, then found that the bigger ones made everything feel smoother, then added weight. Then found the added weight added inertia to the engine, then made a larger diameter for performance.
The whole thing is just an experiment anyway. All the way from the Model T. try this, try that, HEY that worked pretty good, now if we..............