Do you know what assumptions the settlement was based on? The insurance company is assuming that you can invest this sum and produce X income what are their assumptions of return? It is very difficult to produce a consistent and safe return today and if you invest in stocks or bonds or even mutual funds your equity can be wiped out in an instant as we have seen in the past decade or so. Sometimes it is better to have a guaranteed monthly amount than gamble on a bigger but uncertain return.
One thing you can assume....the insurance company would not be doing this if it were not to their advantage.