In a word, the existing prohibitions are anachronistic. One thing has remained consistent: Banks are in the business of taking and managing risk, have always been and always will be. The change that we must cope with is that technology has changed the ways they take risk, while at the same time improving their capability for managing it.
This creation and management of risk, like much of recent economic change, would have been impossible without the dramatically lower cost of a unit of computing power. Indeed, before the computer, most of the new bank products of recent years were merely concepts, concepts that could not become operational until they were quantifiable.