I consider myself fairly well-informed, but I just don't understand why it is considered good for people to own expensive cars. Are people actually not getting

I consider myself fairly well-informed, but I just don't understand why it is considered good for people to own expensive cars. Are people actually not getting where they need to go, or are they just making their existing cars last longer? They are an "engine of the economy", but what does that mean? Is it possible to have a less wasteful engine of the economy? Can something abstract, like artwork, ever be an engine of the economy? What would happen if the economy only produced stuff that we really want? Would that be bad, and if so, how?