Big banks crush earnings expectations. But how?

JP Morgan Chase World Headquarters on Park Avenue in New York.
Timothy A. Clark | AFP | Getty Images
JP Morgan Chase World Headquarters on Park Avenue in New York.

For the first time in recent memory, Main Street borrowing and spending has been a bigger driver of earnings than Wall Street's trading.

JPMorgan Chase, Goldman Sachs and Citigroup have all reported double-digit declines in trading revenues for the last quarter, as volatility or lack thereof created a void of demand for buying and selling, especially fixed-income securities. While Goldman CFO Harvey Schwartz called a bottom in the activity, which has slowed during the extended period of low interest rates, investors have shifted their focus to other, stronger parts of the banks' bottom lines.

In JPMorgan's case, the bank is seeing client assets rise sharply, and consumer confidence spurs more spending across credit and debit cards. CFO Marianne Lake said she sees high single-digit growth in spending on items like groceries and gas, and double-digit growth in spending on discretionary items like travel and retail.

"Across the board, consumers are spending healthily in all categories," Lake told investors on a conference call.

Read MoreJPMorgan sees profit drop, still beats Wall Street

While JP Morgan brass lamented the slowdown in mortgage borrowing, other borrowing—in small business, commercial real-estate and by high net-worth clients—saw marked increases.

"Consumers, middle market companies and corporations are in increasingly good financial shape," CEO Jamie Dimon said.

While Goldman isn't traditionally thought of as a consumer-facing bank, its "lending" unit saw a 46 percent jump in revenue. Schwartz said he'd even consider acquisitions in the bank's wealth management business— one of its only units where individuals, not corporations, are the client—if the deal added to shareholder value.

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So what, then, should analysts make of a continued slump in trading?

Nothing, according to Dimon, who said predicting it is "a waste of time."