The biggest hurdle seems to be financial. In the New America survey, 87 percent of respondents said not being able to afford to take leave was a reason that men didn’t take it. The United States guarantees only unpaid leave, and not for all workers. The states that offer paid leave generally replace only part of people’s wages, and while more companies now offer paid leave, most workers don’t have it, especially low earners.

But the reasons men don’t take as much leave are not just financial. The survey found that men were more likely than women to be in the full-time, high-earning jobs that provide paid leave, and also more likely to receive full pay instead of partial pay while they were on leave. Yet they were still less likely to take it.

W omen were significantly more likely than men to take unpaid leave when needed, 40 percent versus 28 percent.

A large reason, social scientists have found, is that traditional gender role expectations — that men are responsible for financially supporting families, and women for caring for them — are hard to overcome.

“Part of it is a low level of acceptance of fathers saying, ‘I’ve got caregiving responsibilities,’” said Brad Harrington, executive director of the Boston College Center for Work and Family. “It’s internal, societal, how they’re raised.”

Just over half of men in the New America survey — and a slightly higher share of women — said a reason men didn’t take leave was that caregiving wasn’t manly. Older men were less likely to say this, perhaps because they’ve had more experience caring for elders or other family members, the researchers said.

Nearly half of women said men didn’t take it because they assumed their partners or families would do the caregiving (only a third of men said that was a reason). Eighty-four percent of respondents said men’s decisions were affected by their family’s expectations about whether they should take caregiving leave.