Wow, Howard. This seems like a leading question and I am sure that you were a little provocative because you were looking to stimulate discussion.
I think that whether you are an author selling books (first we have to sell the editor at the publishing company and then we have to sell readers/buyers through book tours, public readings, websites and other stuff) or a business owner promoting other products (or services), we are all in the selling game.
I am not sure on your "quality live dialogue is a more difficult art than 'passive' writing" statement, though. I think that every author prays that there will be a reaction from the reader. We just aren't there to see it.
On your opening line, "Have you ever heard a child say, 'When I grow up, I want to be a salesman'," it makes me think of that third grade classroom scene in the Woody Allen movie, "Annie Hall." If you've never seen it, you should. Maybe no child ever says they want to be a salesperson, but neither do they say they want to be an acupuncturist or a professional organizer or a search engine optimization specialist.
Just the writer's perspective. Thanks for the thought-provoking question.