It's hard to peddle words when that's all you've got in the truck. If you're also selling frying pans or lingerie or rubber bands, well then, that's different, something tangible, and if needed, a definite requirement.
But when you sell words and only words -- everyone already has words. Everybody uses them every day. And though you may come up with a mighty good string of words, compelling or poetic, the customer just might squint an eye, take your measure, and figure -- "You think I was born yesterday? I've heard every one of those words before, said each one here and there, from time to time. And it's never cost me a dime. So don't fuck with me."