What it boils down to is a fundamental argument. Do banks exist to be a source of capital to be efficiently allocated across the economy OR do they exist to enrich themselves through complex financial instruments that they themselves barely understand? Thirty years ago I would have said the former, now though. after LIBOR fixing and a myriad of other scandals it seems that banking has descended into institutionalized gambling.
Ask yourself what you would think if your son or daughter came to you and said they wanted to become an investment banker?