Why is it necessary to have both federal and state compensation plans?

There are four different kinds of federal workers compensation plans. These plans cover work related illnesses or injuries suffered by employees of different federal agencies. The four different plans are: The Federal Employees Compensation Program, The Federal Black Lung Program, The Energy Employee Occupational Illness Compensation Program, and The Longshore and Harbor Workers Compensation Program. Each of these programs are different but some of the things they have in common are that they all provide some type of medical services, compensation for lost wages due to being out of work, and so on. There are differences that pertain to each group also. Say for instance you were an employee of the federal...