Because it's not all "we" who believe that.
From Pope Francis:
“Leaving that [the Supreme Court decision] aside, let’s go back to the issue of abortion, which is a problem.” He said it is important to look at what science has learned in the past few decades: “In this we have to be scientific, see what science tells us today. Science today and any book on embryology, the one our medical students study, tells you that 30 days after conception there is DNA and the laying out already of all the organs.”
He asked, “Is it legitimate, is it right, to eliminate a human life to resolve a problem?” He insisted, “It’s a human life - that’s science. The moral question is whether it is right to take a human life to solve a problem."
The church, like any staid and ancient institution, has to align itself with modern times while maintaining its core tenets. Generally speaking, the Church's stance is still Right to Life. But morality changes as science changes. We used to burn witches to save a town.
source:
https://www.vaticannews.va/en/pope/news/2022-07/pope-francis-condemns-abortion-like-hiring-a-hit-man.html