Why is Marvin Lewis Still the Bengals' Head Coach?

I understand that Lewis, in getting his contract extension on January 4th, got a huge assist from the at-that-time-impending NFL lockout. Keeping your eight-year veteran head coach and assuring yourself some organizational stability in the face of a possibly shortened offseason must've looked much better to owner Mike Brown than hiring a new guy at the wrong time. But why have the Bengals kept a guy who's never been that successful?

Here are the records from Marvin Lewis's eight seasons as Bengals head coach, in chronological order: 8-8, 8-8, 11-5, 8-8, 7-9, 4-11-1, 10-6, 4-12. He's 0-2 in the playoffs. Total record is 60-69-1, counting playoffs.

In addition, the Bengals have been sort of a perennial joke for three reasons: their players' willingness to mouth off to the media, the team's willingness to pick up 'troubled but talented' players who've had run-ins with the law (example: Tank Johnson, Terrell Owens, Pacman Jones, Cedric Benson), and the Bengals' own arrest record. They apparently lead the NFL in arrests during the 2010 season, including 22 during Lewis's tenure.

Also, snake wrangling.

So I'm kind of wondering, why exactly do the Bengals keep Lewis around? Why have they been satisfied with two winning records in nine years? I'm speaking as a Packers fan, and we generally have high expectations for our head coaches (the '70s and '80s notwithstanding). When Ray Rhodes posted an 8-8 record in his first year, 1999, he was fired the next year. When Mike Sherman's team crashed into 4-12 after four straight years of 10+ win seasons and playoff appearances, he was fired instantly. Lewis has hung around for eight years despite everything I mentioned above. So what's the deal here?

My best guess, and I swear I'm trying not to sound like an ass here, is that the Bengals don't have the history or standards that Green Bay does. Seriously. Cincinnati has never won a Super Bowl (they went in '81 and '88, and got killed by Joe Montana both times), and they have a 285-373-2 all-time regular season record. In addition, before Lewis's squad went to the playoffs in 2005, they hadn't been to the playoffs in 15 years. My guess is that occasional division championships are better than no division championships at all, at least in Paul Brown's thinking. The arrests, Chad Ochocinco's mouthing off in the media, etc. are just part of the culture there. That's my best explanation, anyway, for keeping a coach with a pretty mediocre record around as long as they have without much success.