Uber is, of course, far from the only company targeted by activists. There was the campaign to boycott The Gap after the Rana Plaza factory collapsed in Bangladesh in 2013. There’s an ongoing campaign to get consumers to boycott Driscoll’s, the world’s largest distributor of berries. The #GrabYourWallet campaign is trying to get consumers to boycott brands associated with the Trump family. And boycotts aren’t solely a tactic of the left: Conservatives launched an #AnywhereButTarget campaign to get consumers to avoid the chain after the company said it encouraged transgender team members to use whichever bathroom they preferred.

Yet these boycotts are rarely effective in getting most consumers to change their behavior. That’s because consumers are habitual, King said, and have a hard time changing their buying actions. Most people are primarily concerned with quality and price, not ethics. And shopping isn’t something that’s particularly public. People can quietly take an Uber or buy t-shirts made in a sweatshop, even if they know their friends would excoriate them for it.

“Most of the time we consume in private, we’re not held accountable for our actions,” King said.

Americans are willing to sacrifice their money for issues they care about—they gave $358 billion to charity in 2014. But there’s a difference between giving to charity and changing shopping behavior to support a cause, said Julie Irwin, a management professor at the University of Texas-Austin.

“My research shows over and over again that it’s hard for people to make these judgments,” she told me. “It’s really stressful to think about these issues, you might be in a hurry—the marketplace is not super compatible with ethical judgment.”

Consumers are conditioned to be smart shoppers, and so want to pay the lowest price for goods, she said. “Many of us will go protests, we’ll give to charity, but when we’re shopping, it just isn’t how we think,” she said.

For example, Irwin cares about the environmental impact humans are having on the planet, as she wrote in a 2015 article for Harvard Business Review. But when she traveled to Disneyland and was offered the “green package,” which meant the hotel would not wash her towels or tidy her room to save water, she turned it down. “People both want to be ethical and they want to ignore ethics,” she wrote.

Of course, there have been a lot of successful boycotts throughout history. Most famously, the United Farm Workers’ grape boycott in the 1960s resulted in improved working conditions for farm workers. It’s harder today, though, Irwin said. Thanks to the internet, there’s a lot more information out there about products, and about ethical decisions. “There are so many people shouting on social media about something,” Irwin said.

There’s no longer just one company to boycott or one company to patronize. Everyday buying decisions become fraught with larger implications, and many people don’t have the fortitude to keep track of them all and shop accordingly. “People get fatigued,” she said.