What's a bigger commitment: having a child or marriage?

While driving around this early morning with my son, I heard a segment on NPR that made me scratch my head. It was about couples in their twenties who decide to raise a child together, but who do not get married because they feel marriage is too big a commitment at this stage in their lives:

Andrew Felices, 26, and Mellissa Giles, 27, are this new face of the American family. They've been living together since before their son, A.J., was born. He's 2 1/2 now, and he shrieks gleefully as he sprawls on the basement floor with dad, building a train track. The couple bought a cozy condo in Frederick, Md., last summer. A home, a child — but neither is in any rush to tie the knot.

"We're still young," Mellissa says. We're enjoying the time as it is."

I was rather puzzled by this. The implication is that having and raising a child together is less of a commitment than getting married. This is shocking to me. In my moral universe, the sacredness of the obligations one takes on when one decides to create and raise another human being together are much greater than those incurred when one gets married. And it seems to me that the breakup of an unmarried couple who are raising a child together would be much more fraught with difficulties and moral consequences than the divorce of a childless couple.

Now there may be a host of very good reasons why one has a child but does not marry the person one is having a child with. But "not ready to make that big a commitment" seems to me a very strange one. It's like someone who takes out a 30-year mortgage on an expensive house, but gets a month-to-month phone plan because they don't feel they're ready to "commit" to a two-year contract. I'm not sure that's the best analogy, but I think you can get the gist of my bafflement. Once you start raising a child, you can't divorce your child. And that person who you're raising the child with will always be the child's other parent. Do these unmarried parents think that they'll be able to just leave the family if things aren't working out? Yes, there are ways of severing the parent-child bond (adoption, abandonment, CPS taking your kid away). But they strike me a more drastic than divorce, not less.

Now I understand that children can happen unintentionally, whereas marriages (barring intoxication in Reno or shotgun-wielding in-laws) cannot. So one can "find oneself" in a parenting relationship in a way that one doesn't "find oneself" in a marriage (unless you're the narrator in the Talking Heads song "Once in a Lifetime"). But that doesn't change the relative sacredness of the obligations incurred: that child is helpless and utterly dependent on you in a completely different way than your (hopefully) adult spouse.

And the people discussed in the NPR story weren't teenage dropouts who had no control over their lives; the implication of the story was that the decision to have kids but postpone marriage was a conscious one. And that implies it was made within some framework about the relative enormity of those two decisions.

Is my perspective skewed by the fact that I have a low-maintenance wife, but a special needs (i.e. high-maintenance) child? Are there people who really think that they're "ready" for parenthood but not "ready" for marriage? Or am I just a traditionalist because I think the expression:

(levelCommitment(parenthood)) > (levelCommitment(marriage))

evaluates to TRUE if your compiler's moral constants are set within ANSI specifications?

Feel free to comment and discuss. I worry that I may be sounding sanctimonious here. But I really do believe that parenthood should be embarked upon with more circumspection than marriage, not less. Again, there maybe very good reasons not to marry the other parent of your child. But I don't see how "It's too big a step for us right now" can be one of them, when you've already made the great leap.