Few dispute that Chinese tech giants have shaken up retail banking, changing how millions of customers do everything from paying their bills to choosing insurance. But the real disruption may be occurring in a more staid corner of finance—and it's being led by Wall Street.

As investment-banking revenues slumped in the wake of the global financial crisis, traditional broker-dealers found that trading and deal-making weren't cutting it. Steadier money could be made in cash management, the humdrum business of assisting multinational companies with daily liquidity and getting the most out of idle deposits by deploying them in global markets.

JPMorgan Chase & Co.'s treasury services business, its lingo for cash management, hit a 20 percent return on equity last year, compared with 15 percent for its corporate and investment bank. Citigroup Inc., a global leader in this area, posted a return on equity from transaction banking (which is dominated by cash management) in the mid-20 percent range, according to a 2017 investor presentation.