It's because we don't feel comfortable telling people who wear suits and ties and working in high-rises that they're going to jail because they followed the prevailing ethics in their neigborhood. We have no problem sending black people or sweaty guys with ethnic names to jail just because they were joiners who went blindly along with the prevailing social mores in their social group, but we only send investment bankers to jail if we can prove they knowingly sunk lower than other investment bankers. We allow the Wall Street subculture to set the standard for its own behavior, and we consider that the desired normal state of things. Instead of reluctantly intervening to "send a message" once in a while when the corruption becomes too egregious to ignore, we should recognize that the complexity and lucrativeness of the finance industry makes Wall Street a natural locus of crime that requires constant attention. Just like a bad neighborhood or a bus station bathroom.

That means we need a proactive and well-funded SEC, of course.