I never said it was. However, if it's unpaid leave, it's pretty obvious why many would refuse to take it, or not take as much as is available: they can't afford the lack of pay. How are parents supposed to pay their bills if they're both taking a 12-week unpaid vacation? Health insurance doesn't pay your rent. So it seems pretty obvious that for many couples, the woman (who generally earns less, and also usually breastfeeds) will take all/more leave and stay home, while the man will get back to work so their finances don't take too much of a hit.
Of course, for couples where their employers offer equal and paid parental leave, we might see different results.
Why should that be our expectation? The career penalty is a tax on mothers and a subsidy for fathers. That such inequity is normalized is why "adjusting" the gender gap does not solve it.
I'll also do an aside here and point out that generous (paid) and equal family leave ends up being a subsidy for parents and a tax on childless people, and also in a way a tax on single parents.
The Clinton-era FMLA grants 12 weeks unpaid maternity leave. 25 states expand on that, and 25 do not.
> Many fathers probably avoid taking so much leave precisely because it does harm their career.
Some will take it. If utilization rates are not equal, that's not a reason to withhold the opportunity.
> I don't see how it would decrease costs on businesses for parental leave. Health insurance doesn't compensate businesses for having to pay people for time that they spend away from work
The FMLA only provides for unpaid leave. However, businesses continue to pay for health insurance during the leave period.