Per Kurowski,

You have brought an interesting new angle to the discussion. But one may argue that because commercial banks funds themselves largely by deposits (principal protected), they should largely invest in assets that are also principal protected. For assuming the risk of business outcomes, pass through structures like mutual funds are better suited. You may want to read this short post on "limited purpose banking": http://blogs.stage.cfainstitute.org/investor/2011/07/12/limited-purpose…