Sure, they want to have kids for any number of reasons. To experience the pleasant intensity of fatherly/motherly love, as one example.

The default position probably doesn't involve a positive reason for procreating. All things being equal, people will have sex. So, the absence of a compelling reason not to procreate is sufficient. I don't think many people have kids so the kids can experience self-actualization or whatever. They simply want to have kids and don't think it's wrong.

That the issue is framed as a pro-life/pro-choice dichotomy is already a sneaky move. The default position is of course to defer to the actual people involved and let them make this very personal decision. And the alternative is coercion, not life. Ironically, "pro-life" is the more deliberately chosen position - it's just a choice of meddlers .