A key factor driving the cuts is that job-hopping in finance slowed drastically from earlier years, leaving banks with more people than they expected.

"Attrition has been remarkably low, and that's something that we've just got to work through," CEO said Wednesday. The bank has cut about 2% of its workforce this year amid a protracted slowdown in investment banking activity.

The aggregate figures obscure the hiring that banks are still doing. While headcount at dipped 1.9% this year, the firm has hired 12,000 people so far, indicating that an even greater amount of people left their jobs.

While 's staff figures have been stable at 240,000 this year, there are significant changes afoot, CFO told analysts last week. The bank has already identified 7,000 job cuts linked to $600 million in "repositioning charges" disclosed so far this year.

CEO Jane Fraser's latest plan to the bank's corporate structure, as well as sales of overseas retail operations, will further lower headcount in coming quarters, executives said.

"As we continue to progress in those divestitures … we'll see those heads come down," Mason said.

Meanwhile, JPMorgan has been the industry's outlier. The bank grew headcount by 5.1% this year as it expanded its branch network, invested aggressively in technology and acquired the failed regional lender , which added about 5,000 positions.

Even after its hiring spree, JPMorgan has more than 10,000 open positions, the company said.

But the bank appears to be the exception to the rule. Led by CEO since 2006, JPMorgan has best navigated the surging interest rate environment of the past year, managing to attract deposits and grow revenue while smaller rivals struggled. It's the only one of the Big Six lenders whose shares have meaningfully climbed this year.

" All these companies expanded year after year," said Marinac. "You can easily see several more quarters where they go backwards, because there's room to cut, and they have to find a way to survive."

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– CNBC's contributed to this article.