Self-publishing used to mean forgoing the resources of traditional publishing and running your entire independent enterprise by yourself. Thanks to technology and the increased connectedness allowed by the Internet, indie authors now have access to experts, marketplaces, and readers. What's not to like?
Authors want to manipulate readers' thoughts — this is why we read, after all. We love getting swept away into new worlds, with new people and ideas. Getting a reader's thought map is a great way to hone this skill.
Of course, not every self-published author is going to hit the bestseller list. But, you have a better chance if you apply some of the lessons taught by those who have.