As an officer, certainly you've worked with people in this situation before so I'm sure you probably have your own answers to this. I'd imagine you've seen some of this.
Here is my short list:
1) Some people have babies LITERALLY for the oxytocin hit. Some people are unable to feel that level of love and connection with another being. They love their newborns because that is something they can love. It doesn't talk back and it's just so cute! In my experience, these people tend to have FAS (but that's just my experience).
2) Didn't want to get an abortion...or, as is apparently now probability, they cannot get an abortion
3) Once upon a time, their life had more hope. Now, not so much. Circumstances change. Imagine if that single parent ends up hospitalized or one of their children breaks their leg.
4) Once upon a time, they were a 2 income family, now dad is gone (or mom, I suppose).
5) Babies intrinsically are a sign of hope.
6) Some people just have always wanted to be a mom and don't recognize EVERYTHING involved in that and are then selfish about it and don't think about the child's struggle. But...at LEAST those children will be loved. That's good.