Because ...
1. Who is going to take care of the unwanted kids? You? Republicans (not all, but much of the pro-life force) don't want to pay up for welfare either.
2. It's none of your fucking business what others do with their bodies.
That being said, I don't really care that much. It will really only hurt women in red states. Good riddance. You get what you vote for.
It's more about them having to live in country that condones abortion than it is about the "babies being murdered" who, once they're born, they could give a shit less about.
It is all about their religion, aka all about power and control. Most women who get abortions don't do it because they want to, anyway; they do it because they're desperate, for one reason or another. I think there should be limits on abortion, but why would you ban abortion pre-consciousness? It's no different than killing a plant or some other non-conscious form of life. Makes no damn sense ...