Economic growth would come from knowing your work force would always have access to healthcare as required to cure or treat whatever may arise so they can't return to work. Also it comes from saving money on the expensive ER treatments that people without health coverage get, waiting for a condition to become life threatening and then paying for treatment is not as cost effective as treating it when its just developing.
If you don't care what the SCOTUS says why did you mention them earlier as support for your position? Seems hypocritical to pick and choose what court rulings to give credence to and which to ignore. Also those people do get something in return, they get healthcare because regardless of whether or not you buy health insurance you will at one point in your life need health care and some of that cost will come from the government. No one exists in an island where all their health care is free of government money.
Also here's that law from 1792
Militia Acts of 1792 - Wikipedia, the free encyclopedia
"Militia members, referred to as "every citizen, so enrolled and notified," "...shall within six months thereafter, provide himself..." with a musket, bayonet and belt, two spare flints, a cartridge box with 24 bullets, and a knapsack. Men owning rifles were required to provide a powder horn, 1/4 pound of gunpowder, 20 rifle balls, a shooting pouch, and a knapsack."
So we've got over 200 years of history of the government making people buy things for the greater good, in this case its defense, in the ACA's case its health care.