When it comes to financial stocks these days, investors seem most concerned about their ability to attract, and hang on to, customers' cash.

For many years, cash was trash, as the saying goes. Savings accounts, short-term Treasury bills and money-market funds paid little yield when interest rates were near zero. And when the Federal Reserve was growing its balance sheet, adding reserves into the banking system, banks looking to hoover up deposits at times just needed to hold out a bucket.

Fast forward to today. The Federal Reserve's rate hikes starting in 2022 reset the bar for what cash could pay out to investors. Fed Chairman Kevin Warsh has talked about shrinking the Fed's largess. And the market is now pricing in higher rates for a longer time.

On top of that, the advance of technology and new forms of banking and money not only add new competitors for cash-neobanks, stablecoins, tokenized or exchange-traded Treasury bills-but make it increasingly easy to switch cash from where it earns little, to where it earns more.

Just this week, the growing interest in Meta Platforms' artificial-intelligence agent Muse once again spooked markets into worrying that cash will be ever easier to move. If it is as simple as directing your agent to find the highest yield, then the inertia that used to protect financial institutions is going away.

While Meta shares have surged more than 11% this week, the KBW Nasdaq Bank index has tumbled almost 3%. Shares of Charles Schwab and LPL Financial were down over 6% and 7%, respectively, on Tuesday. Bank of America, JPMorgan Chase and Wells Fargo were down more than 3% that day, alongside other banks, brokerages, wealth managers and wirehouses-all of which collect customers' cash and earn a yield on top of it.

Many bank stocks this year have at times moved in the opposite direction of interest rates, largely because of concern about rising deposit costs. Though banks can earn higher yields on loans, bankers have also told analysts that it is becoming harder to avoid also having to pass along higher rates to deposit customers.

Cash was also at the heart of the debate over the crypto regulation Clarity Act. The high-stakes lobbying battle about whether or not crypto firms should be able to pay "rewards" to holders of stablecoins, which banks said would compete with yield on deposits, illustrated how vital it is to any flavor of financial company to be able to attract and hold customers' cash.

The declining savings rate in the U.S. is a factor, too. America's personal savings rate dropped to 2.6% in April, the lowest level since 2022. Economists at JPMorgan Chase this week estimated that higher energy prices might have dropped the savings rate by 0.5 percentage point between February and September.

As more people move from saving for retirement to living off those savings, the pressure could grow further. When people spend money in their accounts, the deposits don't go away. But they can move from a lower-cost checking account to a higher-cost commercial bank account, perhaps belonging to a retailer.

And when there is a shortage of savings, higher yields are needed to encourage more saving rather than spending. The boom in AI investment, by driving more bond issuance and faster bank-loan growth, can increase the demand for people's savings, driving equilibrium rates higher.

On top of that, there is changing consumer behavior. Consulting firm Simon-Kucher & Partners found that in a recent survey of U.S. bank customers, 12% didn't have a single, primary bank account. That could jump to 20% by 2029, the firm projects.

"The byproduct of that is that customers in general become more rate sensitive," says Abdul Bhatti, senior director at Simon-Kucher.

Banks and brokerages are also adapting. One thing they can do is shift toward business models that rely on other kinds of fees, in lieu of expecting to earn significant revenue from yields on cheap customer cash.

Robinhood Markets, for example, charges a subscription fee for its Gold service, which gets customers access to things like a 3.6% annual percentage yield on uninvested cash.

Additionally, the fact that yields have now been high for several years, tracing back to 2022, means that brokers already aren't relying as much on cash lying around.

"Compared to the last zero rate era, [the] cash mix is way down for most brokers," Truist Securities analyst David Smith wrote in a note. "It has already been sorted into higher yielding options."

The dash for cash is well under way. And it won't end any time soon.