But many Amazon moms say a missing link is backup day care. Apple Inc., Microsoft Corp., Facebook Inc. and Google parent Alphabet Inc. all provide backup day care benefits. As millennials age into parenthood, family-friendly benefits have consistently ranked as the most coveted perks. Amazon differs from other big tech companies in that its workforce includes software engineers in Seattle as well as warehouse employees in Kentucky. Still, backup day care as a benefit is moving beyond white-collar office workers. Starbucks Corp. last year introduced the perk for baristas. Meanwhile, universal childcare is emerging as a potent political campaign issue.

Childcare is directly connected to the gender pay gap in America, a complex social issue that can perpetuate itself when families decide who should stay home from work to care for ailing children, says Katharine Zaleski, co-founder of the gender-diversity recruiting firm PowerToFly. Since most men in the U.S. earn more than women, she says, moms are more likely to stay home when children are sick since the loss of the father’s income is more likely to be detrimental to the family budget. Providing backup day care helps protect women from having to choose between their children and their careers, Zaleski says.

“It sends a message about creating an inclusive workplace where women can thrive, because the company recognizes this undue burden has historically been placed on women,” she says.

Bezos has seldom championed social issues. Amazon followed the pack in 2015 when it expanded maternity leave to 20 weeks from eight and allowed paternity leave for the first time. The company in October pledged to pay all of its warehouse workers at least $15 an hour, after presidential hopefuls Bernie Sanders and Elizabeth Warren held out Amazon workers on food stamps as an example of the need for living wage protections. Amazon in the past two months has added two women to its male-dominated board of directors, following years of criticism from activists.

Still, Bezos isn't easily persuaded to enhance benefits simply because they would help staff, according to people familiar with the company’s internal deliberations. He is notoriously frugal, insisting that employees fly coach and eschewing the free meals common at other tech companies and instead giving away bananas from little kiosks around the campus. This is why, the people say, it’s more effective to argue that denying the benefit hurts the bottom line by increasing recruiting costs.

Several years ago a group of Amazon employees pushed the company to provide gender reclassification surgery as part of its healthcare package. They initially argued that providing such a benefit would project an inclusive workplace image and help recruit top talent, according to a person involved in the campaign. Human resources advised the group to instead argue it would help the company save money, the person says. Subsidizing gender reclassification cost less than recruiting a senior engineer, making it a financial issue rather than a social one. “This was never a decision about money,” Amazon said in an emailed statement. “It was a decision to do the right thing for our employees.”

Studies demonstrate that mothers continue to bear the brunt of childcare responsibilities and companies that provide day care support can reduce employee absenteeism by as much as 30 percent. That’s the kind of evidence that can resonate at Amazon, but the plight of working mothers is largely hidden, according to current and former employees who spoke on condition of anonymity.

Some don't mention having children or display family photos on desks in fear of being labeled a “distracted mom” unable to tackle important projects. Others  are loath to  be the first to leave even though the day care facility is about to close. Some mask their obligations. The vomiting, feverish child at school becomes a “last-minute conflict” in the meeting cancellation email to co-workers. Some new mothers don’t seek promotions, doubting they’d get the support needed to take on a new role. In Seattle tech circles, friends of parents taking jobs at Amazon often joke: Leave a photo at home for your children so they don’t forget who you are.

The company’s unrelenting demands created a pattern in which men with stay-at-home wives advanced to leadership positions and women often see their careers languish or they leave, the employees say.

One former Amazon worker says she arrived at 7 a.m. each day to avoid the distracting sounds of her mostly male colleagues shooting Nerf guns and bouncing tennis balls off the wall. She was warned about the “bad optics” of leaving before her colleagues, so often stayed until 7 p.m. She spoke with HR about her difficulties and says they suggested she start looking for another job if the culture wasn’t a good fit.