One stereotype I've internalized is that the person who gambles is the schlub who's down on his luck or just going nowhere. What does he have to lose? -- he might as well risk it. I recall two episodes (at least) from one TV show alone featuring this narrative: The Simpsons had Homer betting on a dog race to pull in some Christmas present money during a bad year, and Krusty the Clown bet his last couple of bucks on a horse after a long financial slide.
Therefore, when more and more people feel that they're desperate, unlucky, or going nowhere, they should start gambling more. Conversely, when things look up, they should feel little need to gamble.
I don't know where this story came from -- probably from before the Industrious Revolution (when Europeans started to exhibit more middle-class traits like thriftiness and low time preferences). It's probably like the tales about upper-class murderers -- these plots used to be realistic in the 14th century, but now TV shows like Law & Order are just keeping alive a fairy tale. This also reflects the genetic and cultural change of the Industrious and Industrial Revolutions -- those violent upper classes killed each other off, and they were replaced by the more peaceable nation of shopkeepers.
At any rate, we now know that this gambling story isn't true. During the recent orgy of boominess, people were gambling, speculating, and leveraging like crazy. There was even a hit TV show set in Las Vegas, an epicenter of the housing bubble, about celebrities playing Texas Hold 'Em! And as it turns out, casinos and lotteries are getting hammered as consumers are saving more to pay off their debt after a long leveraging binge that began in the early 1980s. (Everyone who wants to sound cool slams the '80s as a decade of excess, but that continued unabated right up until the current economic meltdown.)
Some narratives make intuitive sense, and may even have been true at some point. But given how radically the world has changed in the past several hundred years, it's worth not taking those stories for granted. We need to update our picture of the world by checking the facts.