As long as people keep bringing them up as just another reason to legislate abortion on demand, I'll keep responding to them. It's as easy as that.
You're probably also aware that a primary argument for the pro-life position is that there's another body in that woman, and it's not very easy to discard its bodily autonomy if you really intend to make bodily autonomy your lynchpin. You're probably also familiar with fetal viability arguments, since a healthy second body outside the first healthy body sort of defeats autonomy uber alles arguments. I've heard enough bodily autonomy arguments to know some claim the head may be crowning and it's still a lump of cells at the mercy of the whims of the owner of its temporary home. I also don't want anyone to get the idea that there's nothing to be done to arrive at a livable compromise--I think a lot of wrestling legislatively can arrive at some 12/15/20-week system for legality simply because a ton of Americans recognize the two-body problem and are capable of weighing their rights.