If you want to be published but aren't, why not?
I've found from the responses for my nonfiction book The Mindset Revolution that my "platform" must be considered huge to start. Most agents state they won't take someone on unless that's the case due to increased difficulties with finding placement at publishing houses. You'd be the expert on this topic though and perhaps said agents were just completely disinterested in my content. In other words, I'm not unpublished due to lack of trying.
I guess I just haven’t found the right agent yet. I actually haven’t submitted very many book proposals to agents yet. (Maybe a half dozen) I am learning a lot about what the agents are looking for as far as sample chapters, outlines, etc… A couple asked to see three chapters. I’ve been following your book, “Write the perfect book proposal” closely. I’ve been working on book proposals for some time now, at least five years and the book has always been right here, on my desk. My query letter, chapter outlines and sample chapters are good, I wasn’t ready with three full chapters though. Recently I’ve been doing a lot of editing too. I just read the book, “A dash of style. The art and mastery of punctuation.” That book has helped a lot. I’m looking to make a big push for agents in about 2-3 weeks; I’ll have two proposals ready by then.
So to answer your question, I guess I spend too much time editing and re-writing and not enough submitting.