On or about 1955 cars went to 12V systems. And, all the cars made, up to say '70 had ballast resistors, or resistance wires.

Millions and millions of cars made and no one thought to up grade the coils to take 12VDC? Not parts manufactures, engineers at car companies, nobody?
All of them had insufficient coils that needed to be protected by a resistor.

But yet, you can take one of those coils, hook it up to an MSD, and blow enough energy out of it to make the old points spark look sick. And it will last forever? Huh?

I think the resistor is there to either protect the points, or some ECU's.

But, that is just my opinion, and I've stated it before.