Well, it's because people can only deny the common sense for so long before they realize that simply pretending a person isn't a person because they're younger makes no sense.
People start feeling like they're doing what it actually is, killing little innocent humans.
However, to be honest, it may very well be that people are simply using morning-after and week-after drugs more that kill the child conceived, and liberals, who are literally just about the only ones actually doing abortions, don't count those as abortions.
Remember, that whole thing. They tried to say that it's not abortion when the child hasn't implanted into the uterine wall yet.
Liberals live in a world of delusion where they use words instead of reality to convince themselves. They call a child under the age of birth a fetus because they think that the word fetus somehow magically changes what the child is.
They refuse to call it abortion because the child never implanted in the uterine wall and technically started the pregnancy, therefore it magically changes what week-after and morning-after pills actually do, which is kill the conceived child not yet reached the uterine wall.
It's the exact same thing they do with every reality that contradicts them. They are literally the polar opposite of the liberalism of our founding fathers and Lincoln's day Republicans, yet they think that because they call themselves liberals, it makes them magically just like the founding fathers or Lincoln's day Republicans.
Even though liberals are progressing us into an age of government having all of the power again, like they did before the Revolution, into a day where some are treated special, like they do with blacks, into a day where some are legal to murder, like with children under the age of birth, or popular consensus today is under the age of 24 weeks in the womb, into a day where religion is controlled and regulated by government, into a day where people are not allowed to disagree with accepted establishment norms, i.e. the left wing, into a day where we trust the government and be grateful to the government for all we have,
They still think that because they call themselves "progressives," which traditionally means the exact opposite of all of that, that means that they are somehow better and "progressing" towards a better day with more freedom . . . . somehow.
Liberals are big on words and very low on facts and reality.