One of the main advantages to self-publishing is developers get to keep a greater proportion of the revenue from the sales of their games. The main disadvantage is the developer has to deal with a host of production and marketing headaches that are normally accomplished by a publisher, like development costs, advertising, packaging, and, most importantly, distribution. If the developer has enough money to produce, publish, and market a game, with a realistic and reasonable expectation of recovering those costs through sales, then self-publishing could be the best way to go. However, the sad truth is that most developers rarely have enough cash to do all of these things. Since key industry publishers, such as Electronic Arts, Activision, and a precious few others, control or influence most of the industry's distribution networks, getting a major publisher to back a game is generally cause for joy.
Retailers have relationships with specific publishers and independent distributors.
If a developer does not have a link to a publisher or distributor, the developer generally has no means of getting games to a major retail outlet. Let's say you create a first-person shooter based on Norse mythology called Lords of Valhalla. On the downside, by going with a publisher, you may only receive a 10-20 percent royalty based on the wholesale price of all units sold. Although you sold 100,000 units with your publisher, depending on the terms of your publishing contract and the price per unit, you may have been able to make more money selling a smaller number of copies as a self-publisher. The above is a very simple example.