You can clean cast iron with soap of course, if you're using it often and well you don't have to. Most of the time all I need to do is wipe it clean with a paper towel and let it be like that until I use it again a few hours later.
I figure this is probably what those "dirt poor southerns" were doing too, since it's simple and effective.
I’m mostly wondering about why the “cast iron” part is relevant. If a wipe is enough for that type of pan, isn’t it good enough for all of your pans? If there’s food stuck on, you’re obviously going to do whatever it takes to remove that. But when that isn’t the case, is a simple wipe good enough?
Copper and stainless steel invariably get food adhered to them very well. (Try cooking eggs in stainless steel) A properly-seasoned cast iron pan is, in many ways, like a teflon-coated one. So, I suppose my comment would go for teflon-coated pans, as well.
If I still used stainless steel, you bet I'd be soaking them overnight then scrubbing the hell out of them in the sink the next morning.
I think it really depends on how often you use it. If you use it every day, then I think wiping it down (maybe with a bit of added oil depending on what you just cooked) is more than adequate most of the time. If you use it once a week then put it in a cupboard before using it again, then you'd want to clean it more thoroughly because you might get stuff growing on it otherwise.
I figure this is probably what those "dirt poor southerns" were doing too, since it's simple and effective.