Supplementing your existing copyright with a Creative Commons license can help you manage your copyrights and share your works without losing your rights. What, though, are some of the specific benefits to you as a creator of artistic or scholarly works?
Remember that adding a Creative Commons license to your work doesn't take the place of the copyright that you already hold.
Until the Copyright Act of 1976, the U.S. government required creators to register for copyright protection. If the new creation was not registered, it automatically entered the public domain. Since 1978 (when the Act took effect), a new creation falls under copyright protection automatically, as soon as it is fixed in a tangible form. Furthermore, this is true even if the author does not want or need to reserve these rights.
Additionally, the copyright term has been vastly expanded since the first copyright law was established in the U.S. Constitution. In 1790, copyright protection was in force for 14 years, with an additional one-time term extension of 14 years possible if the creator took steps to secure it. Since 1978, the maximum term is the life of the creator + 70 years for single-authored works, or up to 120 years after creation for other types of authorship. The effect of these changes is to vastly reduce the number of works entering the public domain.