In immigration court deportation proceedings, those who have a lawyer win their cases 46% of the time, compared with 16% for those without a lawyer. These people have no Fifth Amendment protection against self-incrimination, no guarantee of legal representation, and less due process protections that would be enjoyed by litigants in other courts.
Moreover, the laws are stacked against immigrants in deportation proceedings, as the immigration judge has very little, if any discretion. You can have lived a model life in the US for many years, made significant contributions to your community, have the support of the community, etc. The Judge can only consider these fact in very limited circumstances.