Walking through a Costco (NASDAQ:COST) several years ago, I thought I'd glimpsed the limit of supersized American shopping culture. There, nestled in between cases of beer stacked to the ceiling and plasma-screen televisions by the pallet-full, was a long row of Liberace-white grand pianos. I half expected to round a corner to find a row of shiny black Mercedes.

So far as I know, the discount giant isn't selling luxury cars by the gross yet, but it is peddling home mortgages. As absurdly entertaining as that might at first seem, it's a startling development in the financial sector -- one that big mortgage originators like Bank of America (NYSE:BAC), Wells Fargo (NYSE:WFC), and JPMorgan Chase (NYSE:JPM) shouldn't take lightly.

Somebody please sell me something
Since the financial crash, consumer credit has tightened for at least two reasons. It was defaulting mortgage-backed securities, packed with defaulting subprime loans driven by loose lending standards, that officially kicked off the crash, so lending standards had to be tightened up. And as regulators have called for higher capital reserves, banks have been lending less and less in order to meet them.

But this is America, and when people are determined to buy something, someone will find a way to facilitate it. So Costco now offers home mortgages. It also sells car and home insurance. And Costco isn't the only retailer edging into the financials sphere. Last month, Walmart began offering a prepaid credit card, issued in conjunction with American Express (NYSE:AXP), that's not connected to a bank account.

Finance hates a vacuum
"The banks are going to scream bloody murder when retailers try to obtain banking charters," shopper behavioral researcher Paco Underhill recently told The New York Times. Yes, they are. But it's hard to blame retailers for dipping their toes into financial waters: There's money to be made. Americans will not be denied their debt. And if the banks can't, or won't, lend to a credit-addicted populace, then some other entity will.

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This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.