Because so many so-called Catholics are just as pro-abortion as Obama is. That is a product of the “Seamless Garment” theology that was in vogue up until very recently. So-called “social justice” was viewed as equally important if not more important than being pro-life.
Admittedly, this would never be expressed in so many words.
But if you think back not all that many years…just compare how many homilies you’d hear about “social justice” issues vice how many you’d hear about “pro life” issues.
Not every parish. Not every diocese. But a whole bunch of them.
Or look through your kid’s CCD textbook. Compare how much coverage is given to pro-life issues there versus “environmental justice” or the like… (I am thinking about the “Call to Faith” series…your mileage may (and I hope does) seriously vary)