Not to mention, when the transmog system was first announced, lots of people said that "everyone" will be running around in specific iconic tier sets, like Judgment for paladins or Avatar for priests. Those were quite popular right at the start, but now I rarely see them. People like to be unique and they like to vary their looks. If old legendaries became available for transmog, we might see a lot of them at the start, but then plenty of people would get bored and switch to something else.
Right now, the art is doing no one any good as an icon in banks.