Yes, it's a "burden" on employers that their employees are not automatons who have no purpose in life beyond ensuring their uninterrupted availability 9-5 each weekday. Humans get ill. Humans reproduce. Humans change jobs. Humans get distracted by their affair with their secretary and fuck up the smooth running of the business. If you don't want to deal with that, don't hire a human. But if you want (or need) a human brain to do the work, then you need to accept the issues that come with humans and a well-functioning society depends upon a safety net when people need to be temporarily unavailable for work.
While holidays and occasional sickness is part and parcel of hiring a human being, a year off due to having a baby is not. It's true that humans procreate, but how is that relevant in the context of a employer-employee relationship.
Humans also buy clothes - should it be down to the employer to buy nice shoes for their employees? Humans take sabbaticals to better themselves - is the employer's responsibility to support that?
In so far as the employer-employee relationship goes, the employer should only be obliged to support issues which are extensions of work.
If you want your employees to commit to working only for your company, rather than hiring themselves out to whoever is willing to pay them the highest rate on any given day, ditching your task mid-project, then you have to give them some sort of commitment back in return. Which is, you won't fire them if they get ill, have an accident, or have children (something which the entire of society depends on people to do). Otherwise hire, and pay, for a day-rate contractor.
Actually one could argue that in return for the employee committing to show up for work every day, the employer is committing to pay them, regardless of whether they were needed or if the company made money that week. Committing to support every life choice of the employer goes far beyond the remit of employer-employee relationship.
If your company budget is so precarious and poorly run that you can't afford to employ women in case they have children, and can't hire people with disabilities in case they are unable to work, and can't hire men who might want to take paternity leave, then ultimately it's you who will suffer long-term, as all those talented people will work somewhere else, leaving you with the industry's dross that couldn't get a job at a better employer
There are enough talented people who don't fit into the above categories. If it weren't that way, why would women need discrimination laws that prohibit companies hiring talented men over talented women just because of their gender?
Fact is most companies could run very well without the legal obligation of keeping an employee's position open for a year while she has a baby. In fact they do run very well in countries that don't have this anti-business protection racket.