Not always.  Sometimes, you do not need a lawyer to win.  But, if your case is complicated, an advocate can help you.  The advocate does not have to be a lawyer, even for a fair hearing.  To file a lawsuit in court, you may need a lawyer.  Sometimes you may file a lawsuit on your own.  If you file a lawsuit on your own, called in pro per, you may be able to get help from a legal aid program.