more of a commitment?

I have a few friends who live with their bfs and are currently pregnant. when the topic of marriage comes up, they all freak out and say NO! they say they would have kids with her bf but never get married because that's too much of a commitment. and I was a little confused? isn't bringing a life into this world more of a commitment? do you guys agree that marriage is more of a commitment than having kid(s)?

and before I get the- "marriage is just a piece of paper," that's NOT what I'm referring too, I'm referring to the part where they say its MORE of a commitment.