On the mostly unrelated "women not wanting to be pregnant" note, I completely understand that and say more power to women who know that they don't want to procreate. I think a lot of the problems we have with parents being shitty is because they give in to the pressures of society or their partner to have children (on either side) when they really don't want to. I don't think even a biologist would argue that people who don't want to be pregnant or contribute to procreation should because it's our assumed instinct or responsibility as members of a species or whatever. Some people just don't want to have kids. Those people should not have kids. Pretty simple.
On the subject, now. I think the problem with marriage is not exactly a problem with marriage, per-se, but a problem with how we view relationships in general. We have all probably fallen victim to Staying Too Long in a relationship in which we were unhappy, out of some stubborn need to prove people wrong or stupidity or foolish notions of love or naivete or whatever it is that caused us to abandon our own happiness and satisfaction to stay with this person whom we should have left much, much sooner (or never devoted ourselves to to begin with). The opposite is also true. One major blowup, one difficult situation, money problems, miscarriage, whatever - and we bolt. Why?
I think it's a problem with self worth. We don't realize that we OURSELVES are worth it. That our own happiness is important. So we stay in situations that we should not, or leave situations that really do make us happy. To make things easier, to minimize conflict, to make someone else happy. Because, of course, all of these things are more important than doing what makes US happy.
To address what Gorix said about the separation of church and state - it's already that way. Religious marriage in the US is technically two separate things happening in the same ceremony. The religious ceremony, and the legally binding contract. People who want to be married but want a secular ceremony, or or no ceremony at all, can file the same paperwork and be married just as legitimately as people who participate in a religious ceremony.
Yes, gay people should be able to get married. As should anyone else who wants to be married, as long as they have the mental faculties to sign the form.
I support marriage, for people who want to be married. I can't wait to marry Sweeney. And I know, beyond any doubt, that I want to stay with him until I die (because let's be honest, I'm going to die first (the kind of dead where you stay dead, Joe

)).