Just FYI, you do wash cast iron, you just don’t use detergents on it. One common method is to dump a handful of salt and a tiny splash of water into the pan and start scrubbing. You can use a gentle dish soap, but I’d avoid using the dishwasher, because those detergents will be a lot stronger and will actually ruin the seasoning (as well as linger on the surface and end up in your food, which is also bad).
Modern soaps/detergents don’t contain lye, which is what ruins the seasoning. It’s the humid drying of a dishwasher that causes it to rust. Nothing to with the detergent.
As a mild ph adjuster, you would have to soak your cast iron in Dawn (platinum only) for hours, which would ruin your seasoning no matter the detergent used.
Detergents are basic because that works wonders on greasy stuff. When oil polymerises it won’t be susceptible to basic substances anymore but will react to acids. (Unlike acid and oils which don’t really react with each other – think vinaigrette separating in the fridge.)
Washing a cast iron pan with detergent will clean it from unpolymerised oil.
Cooking e.g. tomato based sauces in your cast iron pan will strip it of the polymerised coating (might impart flavour too).
Cleaning kitchen tiles near your stove is sometimes easier with acidic cleaning solutions as well. Just be careful with the caulking which will brittle over time from using acids.
