That's a good point. But, since this is a Writing Forum, it's also the very type of thing aspiring writers might want to ask about. An accomplished author would have no need for such instruction, while one that is still learning would be hungry for it. Still, I've seen the work of plenty of published authors that proved they're terrible at creating interesting metaphors. It's sad, really. Language is such a beautiful thing and it would make sense that any author would want to paint with an interesting flare, rather than use a tired brush.