In F3 there was the natural history museum that was a refuge for them. They were everywhere. The bartender in megaton was a ghoul. In NV there were Ghoul NCR rangers overlooking Cottonwood Cove. Maybe I’m misunderstanding you/it’s a definition thing, but I can’t imagine how you could have missed them.
I suppose I don’t remember them, I think they were just not very memorable maybe. I just remember the ones in the first two Fallouts. We’re talking about the same thing that’s for sure though.