1970 Duster regulator and resistor

I can understand the resistor going there to the can if you are using modern ignition like MSD, but why would you not use the voltage regulator if you are still using original Alternator?

I wouldn't run any mopar ignition or factory style alternator in any of my mopars. Been there, done that. HEI or MSD and a single wire alternator. Clean and effective