Reappointment of IAS officer after retirement ?

Why Govt. reappoint IAS after retirement? Why not government increase the retirement age instead of reappointment? Why not reappoint group B, C & D employees after retirement? Why not government give employment to the youngsters ? Unemployment is at a high peak but neither centre government nor MPs of any party are  worried & thinking about it. Serious urgent concern.

Satvinder Sachdeva