Your last statement is most likely not true for Europe.
So in the end it comes down to cultural preference. If the majority prefers a certain way of doing things, it makes sense to back it up with legislation to harmonize it and make it safe for the individual (in this case, for instance, guaranteeing you to get your old job back after maternity leave).
I mostly agree with your points in this thread, but this statement might be incorrect. Earlier, Swedes with X income did not choose paternity leave. Now Swedes are given X+leave benefits and therefore do choose paternity leave. Although they were always free to choose, it might be the extra bonus that nudged them into taking the leave.
Also, people are not economically rational. They will blow all their money and then, when they have a kid, not have enough to support themselves for an extended leave. Few people have the self-discipline to save for anything in the distant future, including retirement.
You are free not to receive the benefits. You are not free to avoid most of the costs. For anyone who values the benefits at less than the full costs, this policy is harmful.
So in the end it comes down to cultural preference. If the majority prefers a certain way of doing things, it makes sense to back it up with legislation to harmonize it and make it safe for the individual (in this case, for instance, guaranteeing you to get your old job back after maternity leave).