One of the most disturbing realities of the 2008 financial crisis is that no Wall Street executives have been held accountable. After searching more than five years for the reason some people have gotten away with the financial equivalent of murder, I think I have finally figured it out: It’s the revolving door, stupid.

The chance for senior government officials to make millions of dollars after their public service ends convinces them -– subliminally or not -– to pull their punches. No doubt that’s why Jimmy Cayne, the former chief executive officer of Bear Stearns & Co., continues to enjoy playing bridge and golf, his $400 million-plus fortune, his sprawling mansion in Elberon, New Jersey, and his duplex at the Plaza Hotel.

It also explains why Dick Fuld, the former CEO of Lehman Brothers Holdings Inc., was able to form Matrix Advisors to consult on mergers and acquisitions, even though he had been a trader, not an M&A banker. Even if the firm has no clients, it doesn’t much matter: Fuld testified before Congress that his 2000-2007 Lehman compensation was about $310 million. He later conceded it could have been $350 million. The real number is closer to $520 million, according to people who prepared and studied Lehman’s public filings.

When Stan O’Neal resigned from Merrill Lynch & Co. in 2007, less than a year before it almost went bankrupt, he was given a parting gift of $161.5 million and a board seat -- which he still holds -- at Alcoa Inc.

The dossier of executives being rewarded for bad behavior goes on and on. The question is: Why have prosecutors allowed Wall Street executives to slither away into the 1 percent, or one-tenth of 1 percent, without paying a financial penalty or serving time? After all, as the Financial Times reported, about 3,500 bank executives went to jail after the 1980s savings-and-loan crisis, which wasn’t nearly as devastating as the 2008 debacle.

In contrast, not a single bank executive is wearing an orange jumpsuit today. “The Justice Department failed,” former New York governor and attorney general Eliot Spitzer told Frontline a year ago. “They didn’t ever try to bring together one coherent narrative, laying out the entirety of the story against one of the major players and demand sanctions that are meaningful.”

Not even the oleaginous Angelo Mozilo, the former Countrywide Financial Corp. CEO who walked off center stage with a net worth of about $600 million, has spent time in jail for creating and selling billions of dollars of squirrelly home mortgages that found their way into the securities that Wall Street sold to investors.

The lone civil case that occasioned a victory lap for the Securities and Exchange Commission was against Fabrice Tourre, the former Goldman Sachs Group Inc. vice president who was guilty of nothing more than following orders as a foot soldier in the Wall Street army. Tourre is currently appealing his 2013 conviction in this ridiculous case; I hope he wins.

In 2011, as part of a profile I wrote about him in Fortune, Preet Bharara, the U.S. attorney in the Southern District of New York, explained why he hadn’t prosecuted any Wall Street executives. He supplied the usual pabulum about how he wanted nothing more than to bring such cases, but that piles of subpoenaed documents revealed no evidence of prosecutable wrongdoing. If that’s true, then Bharara should release the evidence publicly so that the American people can see what he has seen.

So why do I blame the revolving door between law enforcement and the private sector for the lack of justice? Consider Lanny Breuer, the former criminal division head at the U.S. Department of Justice. He told the New York Bar Association that worries “literally keep me up at night” that innocent workers and markets might suffer if he indicted Wall Street firms. Breuer left government last year to return to his partnership at the Covington & Burling law firm, where he is paid millions of dollars a year. You don’t have to be a genius to figure out how this game works.

When Robert Khuzami, the former head of enforcement at the SEC and a former general counsel of Deutsche Bank in the Americas, leaves government for a $5 million-a-year job as a partner at Kirkland & Ellis, you can see what’s going on.

When Tim Geithner, the former Treasury secretary, takes over as president of Warburg Pincus LLC, the private-equity firm, even a high-school dropout can discern a pattern.

When the general counsels at JPMorgan Chase & Co., Bank of America Corp. and Deutsche Bank AG -- Stephen Cutler, Gary Lynch and Richard Walker, respectively -– previously had been directors of enforcement at the SEC, the picture becomes perfectly clear.

Last week, we got more irrefutable evidence when Julius Genachowski, the former Federal Communications Commission chairman, joined the Carlyle Group as a managing director to work on media, telecom and technology industry buyouts. Can you say ka-ching?

The promise of the corporate honeypot for departing government officials has been a reality at least since 1968, when Treasury Secretary Henry Fowler became a Goldman Sachs partner. Unless, and until, the revolving door between Washington and Wall Street is bolted shut, I think it’s safe to say the American people will continue to be ill-served by those empowered with the hallowed role of prosecuting wrongdoing.

(William D. Cohan, the author of “Money and Power: How Goldman Sachs Came to Rule the World,” is a Bloomberg View columnist. He was formerly an investment banker at Lazard Freres & Co., Merrill Lynch and JPMorgan Chase.)

To contact the writer of this article: wdcohan@yahoo.com.

To contact the editor responsible for this article: Paula Dwyer at pdwyer11@bloomberg.net.