There are a multitude of reasons why you should hire a defense attorney. Perhaps the most basic reason is that when your livelihood is at stake, you want to ensure that someone with the proper resources, legal knowledge and experience can best represent you.
Another aspect is that with many criminal cases there is the potential for civil ramifications. For example, when you are charged with a DUI in the State of Illinois, you are being pursued by a two headed monster: on the one hand, the State of Illinois through the local prosecution is prosecuting you criminally (the State’s Attorney or District Attorney) and the Secretary of State (currently Jesse White, as of 2012) is pursuing you civilly (statutory summary suspension). In many instances, even if you qualify for the public defender, they cannot represent you with reference to the civil side of it (SSS).