If we try to argue the benefits of such regulation in terms of the commonweal then some will question the contribution of derivatives to the commonweal. However I think that I see the commonweal contribution of sugar futures, for example, in the orderly transfer of intelligence from those with special expertise in such things as weather, consumer taste, etc to those who must make business decisions based on the best assessments of such factors. I would like to see such a description of how risk transfer instruments for mortgages contributes to the commonweal.
Assuming that there is such a contribution I would like also to see how the proprietary price information for such derivatives serves the commonweal, or even just the derivatives market. Is there a similar argument that proprietary information for stock prices would good for the commonweal. I do not now know such an argument. Such an argument might appeal to incentives for producing new sorts of derivatives and the ability of finical institutions to reserve some of the resulting commonweal benefit to themselves. Such an argument seems unlikely to be credible in light of recent experience.