Scandinavians have sane laws about parental leaves : both parents get the same amount. Therefore if you hire someone in the 25-30 age range, there is a high risk of having to do without this employee, regardless of his/her gender. IIRC, the rule is 12 months to be split between the two parents, no part being smaller than 2 months.
The 'down' side is that now us guys also get discriminated against. I've been more or less asked straight out about my family situation at a job interview, and I could tell from the expressions on their faces that they didn't like my answer, and I didn't get the job. Of course it's impossible to say why, as there where a couple of other good reasons why they might have rejected me.
1) You overstate the likelihood of the market driving out discrimination. Racist and sexist discrimination has existed for centuries without the market ever reaching the equilibrium state of no discrimination that would result if people were rational market participants (1).
2) Inevitably people bring up Scandinavia in these discussions, and for good reason. Scandinavian countries have both very generous family benefits (including paternal leave!) and high representation of women throughout the workforce. This isn't dispositive, but it does suggest the situation is much more complicated than the original post would suggest.
All in all, I prefer to live in a world where everyone pays their fair share instead of trying to eke out a couple extra cents of profit by not providing parental benefits to mothers and families.
(1)This is actually an even subtler issue, because it's possible for markets to exist where racism and sexism offer a competitive advantage, due to consumer preferences.