Most rust appears from the inside out, usually caused by trapped moisture in mud which does not get a chance to dry out. However, with the great care that is made to dip and penetrate and especially hidden areas when the car is built, the surface must have been compromised at some point to allow the ingress of water. Sometimes that can be a stress fracture, like at the top of the tailgate where the hings is attached to the tailgate itself.
A 1984 Ballade that I sold to a friend is still being used today and has no rust. However, I have seen similar age Ballades dripping with rust, so you get good ones and bad ones.