I'm sure some necks have been pulled off when doing repairs, and that's a good point. But, at the point you've ripped apart the radiator, you'd know and certainly get a new radiator.
My leak from the gasket was a slow steady loss of 1-3 ozs/week. Once I found that it was leaking, I monitored the level frequently, replaced what I'd lost, and I was fine.
Some here, you know, really can't afford to take care of it as well as they'd like. I just want them to have this information so they can make decisions that work for them. That's all.
Of course, I'm not saying that replacing a radiator is unnecessary or unwise...just that some times, it might not be a necessity.