Copper pots are used for cooking because of the superior heat transfer, but you are not cooking with copper directly. They are "tinned", and this coating needs upkeep. You can't really cook with it directly because it's too reactive with acidic foods.
true, modern ones are electroplated - can still be called tinning in practice although that's inaccurate. It doesn't need anything like the same maintenace as old style.
The point was more that nobody really cooks directly with copper, and did not historically.
