Merck (MRK) CEO Ken Frazier resigned from the White House American Manufacturing Council early on Monday, citing President Donald Trump’s failure to immediately and clearly reject the bigotry on display in Charlottesville, Virginia.

Late Monday, Under Armour CEO Kevin Plank also announced he would resign in protest from the council and Intel CEO Brian Krzanich followed suit late Monday night. And while this then sparked more widespread departures from CEOs and an ultimate disillusionment of the council, it took some time for CEOs to speak out.

Why?

“Given the current environment we are in, there’s more of an expectation that CEOs will be engaged in their political and social environments,” according to Columbia Law professor Eric Talley. “But, individual CEOs may have an aversion to introducing new volatility to the company’s stock price, particularly as companies seem not to be acting in as unified group.”

Indeed, CEOs answer to shareholders before anything else. One of the last things they want to do is get on the bad side of the most powerful person in the world, especially if that person has the power to hinder a company’s ability to conduct business.

Trump responded swiftly to Frazier’s resignation with ire, tweeting that Frazier could now spend more time lowering “ripoff drug prices.”

While Merck’s share price stayed positive on Monday, Trump’s threatening reaction looms large.

On Monday, some CEOs like Goldman Sachs’ (GS) Lloyd Blankfein released general statements denouncing the violence over the weekend. But no CEO other than Frazier responded directly to the President’s delayed condemnation of the white nationalist / neo-Nazi rally in Charlottesville, Virginia. In fact, 22 CEOs remaining on the President’s manufacturing council gave no indication that they would resign in protest like Frazier.

Until today, there have been very few direct actions from CEOs in response to Trump: Tesla’s (TSLA) Elon Musk and Disney’s (DIS) Bob Iger both stepped down from Trump councils protesting the Paris climate deal withdrawal.

Meanwhile, even though tech companies spoke out against Trump’s travel ban in February, CEOs including Apple’s (AAPL) Tim Cook, Microsoft’s (MSFT) Satya Nadella and Amazon’s (AMZN) Jeff Bezos still met with the president at the White House in June.

Even Nordstrom (JWN), which announced in February that it would stop selling the Ivanka Trump brand, clarified it’s decision was based on sales and was not meant as political commentary. Trump blasted the company on Twitter the following week anyway.

This aversion to confrontation comes despite the fact that corporations are seen more as agents of engagement, as shown in recent Supreme Court cases like Citizens United and Hobby Lobby. Talley added that in practical terms, it would be difficult to show that speaking out politically could violate the CEOs fiduciary duty to shareholders.

The resistance to speak out against some of Trump’s policies even comes despite historical evidence that shows a potential benefit of doing so. Decisions by CEOs to embrace progressive political opinions have actually helped stock prices, according to Edward Reilly at FTI consulting, which advises companies on public messaging.

“Well-articulated social activism can still be a risk — but it can also be a competitive advantage,” FTI consulting said in a memo. “This increased scrutiny of CEOs and their management teams by investors and customers, and the greater transparency expected by all stakeholders, has made leadership’s values and sensibilities a major factor in where consumers take their dollars.”

Nicole Sinclair is markets correspondent at Yahoo Finance

Please also see:
Robert Shiller and Jeremy Siegel tell us what they think of each other’s market forecasts
Jeremy Siegel and Robert Shiller tell us what’s next for the economy
Why Nordstrom is beating all of its department store competitors
Stocks have done worse ahead of a conflict than ‘when the bombs started to fall’