When one of the 900 hourly workers at Rent the Runway died, CEO Jennifer Hyman had to reckon with a harsh reality. The dead man's coworkers, a close group that included some of his family members, couldn't take time off to mourn his death or attend the funeral.

If they'd been among the company's 300 salaried employees, it wouldn't have been an issue. Their benefits included bereavement leave, paid parental leave, and time off to care for sick family members, as well as invites to occasional companywide beach or ski days.

It didn't seem fair, and soon after, Hyman decided to equalize benefits across her workforce, making Rent the Runway one of a growing number of companies that are extending benefits to hourly and part-time workers. Almost half of the 391 companies surveyed by the International Foundation of Employee Benefit Plans now offer the same health insurance coverage for all employees. About a third offer paid maternity or parental leave to their part-time workers, too, the survey found.