You seem to forget that there are some very perverse incentives at work for incentivized traders playing with the “OPM” that is actually a contingent liability for the taxpayer. That made a whole lot of sense back when commercial banking was separated from investment banking. Now that the yahoo-cowboy-traders of investment banking are allowed to play with government/taxpayer gurantied funds, there are asymmetric risks and rewards. In the old days, the partners of investment banks (you know– the guys who actually had their money at risk) kept a very close eye on the hired help.