I think it’s partly to do with the (over) use of the phrase “x is an art,” usually meaning “x is a very skilled and hard thing to do successfully.” For example,

I think it’s partly to do with the (over) use of the phrase “x is an art,” usually meaning “x is a very skilled and hard thing to do successfully.” For example, it feels quite natural to say something such as “running a business is an art.” Which is fine, but the natural corollary of x is an art is that whoever does x is an artist. Which leads to this confusion.