The purpose is to provide peace of mind. If appropriate, you may ask the attorney to quote a maximum fee for the case that is being billed by the hour. Please note that there are legal costs involved in litigation, and that ordinarily you will be required to repay those costs even if you lose. Every state limits contingent fees for personal injury and workers' compensation cases. Often, even if you do not qualify for those programs, they can refer you to attorneys who take cases like yours at a reduced rate.
Many large employers provide legal assistance for their employees.
If you are thinking about buying legal insurance, read the policy carefully to see what kinds of legal matters are covered or excluded, what co-payments are required, and whether you are able to select your own attorney. This is usually done where the case is of particular interest to the attorney, and the issue involved in the case is significant to the public interest. Please note that attorneys receive many requests for pro bono work, and can at best take only a few of those cases. You can find the names of attorneys from a variety of sources. You may seek advice from friends, or from your doctor, accountant, or another professional.