I think that most people have a vested interest in abortion being legal.
If abortion is illegal, it means that people have to be more careful about whom they sleep with, and when. It means that if they accidentally conceive a child, they have to become biological parents whether they like it or not. It also creates a burden on the state, as when parents disown (instead of abort) their unwanted children, responsibility for those children now falls upon them; they now have to run orphanages and adoption centres etc.
Almost nobody is better off as a result of abortion being illegal (apart from unborn children themselves, who have no voice in the matter). Clearly, legalising it is the more convenient option for the majority of people.
However, that doesn’t make it morally right. Many people believe it is wrong, because it imposes upon the rights of unborn children, and that they must speak for those who cannot speak for themselves.
Of course we could argue endlessly about whether it actually is morally right or not. But one thing I find refreshing is that it shows that people are able to create and support laws on the basis of what they consider to be morally right, rather than just picking the option that suits them personally.