There are other good reasons to hire an agent besides that of increasing your chances of finding a publisher. An agent will look out for your best interests and make sure the publisher does not attempt to pay you less than you deserve or take advantage of you. If you have an agent he or she will negotiate with the publisher so that you get the highest royalties and advances. They are more knowledgeable about what is fair and within industry standards than you do. An agent will also help you with the contract between you and the publisher to ensure that it is not only fair but within the scope of the law and in your best interest.
Another reason to have an agent is because they have close ties to the publishing community and can help you with book signings and promotion of your novel. The publisher will accommodate some of the promotion and will work with your agent to ensure your book obtains the most exposure, but you also want to be involved in the promotion as well. With the help of your agent you will be able to choose the best places to promote or to work with a publicist to design a package that will provide the best possible promotion for your book.
Agents know what is going on in the publishing world and can determine if your book is going to sell in its present form. For example, if your book touches on a storyline that is currently overused, you are not likely to be able to sell your book to a publisher. An agent can help you make changes to your storyline that will help it sell better, and you if you want to write a bestseller, you want to follow the guidelines of your agent. Certainly an attorney can help you with the legal aspects, but only an agent can help you make sure you are writing a book that publishers will buy.
Many people choose to publish without an agent, and that is certainly possible for authors who are established. You will find a few publishers willing to accept manuscripts directly from the author—in fact, eHarlequin used to not accept agented submissions. However, do keep in mind if a publishers guidelines tell you they will not accept submissions from the author, do not attempt to bypass the requirements—the easiest way to find your manuscript in the slush pile is attempting to make your own rules instead of following the publishers guidelines.