The desire of most writers is to be able to say they are a published author who makes their living from their books. In the past, this implied being published in at least a paperback form, with the goal being hardbacks.
The problem is the odds are against the author. Each day each publishing house receives about 150 submitted manuscripts. This comes out to be about 45,000 manuscripts per publisher. Of the 45,000 manuscripts, only about 2000 will ever be accepted for publishing. The odds are about 1 out of 23 of being accepted at the one publishing house.
Acceptance also depends on very fuzzy conditions. In one reported case, before lunch the manuscript had the green light for the contract to be signed. During lunch, the manager was informed the publishing company finances were down. After lunch, the author was informed the manuscript was rejected. None of this was due to the quality of the story.
In self-publishing you don't have these factors. You remove the speculative nature of the business. You only have the consignment part of the business.
With the standard publishing model, in most cases you have no control over the cover art or description of the book. With self-publishing you do.
Also with the standard publishing model, you have no control over the marketing of the book. As a self-publisher you do. You do all of the marketing.
The standard publishing model treats the published book as an event. This means that in most cases the book is only printed once and distributed to the stores. Once the book has been sold or returned for credit, the book can only be found in a library or in the used book market. This is not true with self-publishing. You can leave the book in the online stores and can continue to have sales long after a book published via the standard model has disappeared from the stores.
If you have only written your story and never published it in any form, with self-publishing you can now have a higher chance of more people being able to find out about the story and buy your E-book. But if you have already published your story, none of the standard model publishing house will accept your story for publication. With self-publishing it does not matter as there is a non-exclusive agreement. This means you can have the story on your web site or a story online site and still self-publish your E-book.
If you have had books published using the standard publishing model, they might not want all of your other stories. Now you have the option of self-publishing those stories. This means they can also make money. If you have an older story which is no longer under contract to the publishing house, you can release it yourself and once again make money off of the story. As an author you now have more options open to you. You can still continue to publish using the standard model as well as self-publish. Thus, there are more options to make money with your stories.
Self-publishing still allows you to say you are a published author with your E-book in the major online stores. You will receive some royalties when your book is sold.
Finally, E-book are greener than standard paper books. No fuel is wasted to distribute the books. There are also no dead trees which gives the nickname 'dead-trees books' to paper books.