It is illegal (discriminatory) to have any policy based on gender. As such, you cannot have a maternity or paternity policy. Thus primary - the parent of the two who will leave their role temporarily as the main caregiver whilst the other partner continues to work OR secondary - the other.
Note though that a health insurance policy in the US will cover maybe 60% of 8 weeks of salary for the birth mother under a disability benefit claim (no joke). If a father becomes the primary caregiver, then the company is paying 100% of that time off, without support. So offering equal carries a cost and guarantees that all your employees, male or female, if they are having a kid will take that time and incur that cost, rather than a % gender of your workforce. All things you need to factor in and cost into a business, especially a small one.
The difference in Europe is that the UK, Swedish or German government subsidies a great deal of that one year. In the US, the company pays for it all, and on top of it perhaps around $2,000 a month for a family health insurance policy for that employee so they can get the birth and emergency care paid for. Again, this is mostly free outside the US. You're hitting up on some societal grade rather than company policy issues. I feel you though, being from the UK and living in the US, it is just insanity. So little care for mothers and parents.
I'm pretty immersed in the field of parental leave benefits in the US and UK, having setup Pledge Parental Leave www.pledgepl.org. Important to get the full perspective on the market in the US. You're taking a crap on a company with extremely progressive benefits across the board, furthermore so, one offering them at a 'meager' size of 50, where the relative cost is much greater than compared to a 'large' company.
It is very easy to make simple comparisons between UK and European standards vs US standards. The fact is that there is almost zero government funding/support for parental leave in the US. The US is the only developed country in the world without any government mandated parental leave standards.
In the US, any company stepping up in this area is doing so of its own volition and cost - again the government gives a company zero funding. In the UK, German, Sweden etc they pick up most of the tab of extended leave. In the US, the only form of support is for mothers through expensive health insurance for the 'disability' of having a child. So before you engage in moral relativism, it's healthy to get the context and the facts. Check out http://www.pledgepl.org if you want to clue up or help fix this situation.