RT rating was a requirement if you intended to use the radio
SoCal, the word "if" is the crux of the matter here, there were places even into the nineties IIRC where you could do a whole PPL course on non-radio aircraft. Admittedly, this would be an unusual option and not sure how many may have chosen to do so. But if you intended to fly something vintage with no electrics out of a private strip, then why not?