For starters, because forcing a woman (sometimes a young girl) to spend several months walking around obviously pregnant, when it's the result of rape or incest, is indescribably cruel. Is she supposed to explain the circumstances of the conception to everyone she knows at work/school and in her neighborhood? Or just let them assume that she can't keep her legs together or remember to use reliable contraceptives? Not to mention that it prevents her putting the horror behind her and starting to recover psychologically, and that delay can have a permanent impact.
But how do you deal with going around trying to explain to others - including your own children, if you have any - that that particular baby wasn't worth keeping alive? Do you understand that if a person becomes pregnant after a rape, and to use the example of a married woman with children. she has others to think about besides herself?
Would you want to tell your children that this baby or that wasn't good enough to be born? Kids don't get that, they will think that if mom can get rid of this baby, then maybe she'll get rid of me. how do you bring them up to believe that abortion is wrong if they see you advocating abortion for some circumstances?
Adoption is a better option if the woman really can't do it, but even then.. if she's got other children already, how to best explain to them that this sibling won't be in their family? They don't really care about biological parenthood, they care about a baby and if you can get rid of one, what's to say you won't get rid of them if you are angry at their father?
Sorry, been there. I went through months of having people look at me like I was lower than dirt because i was pregnant and didn't have my husband around. I went through having even my family think I had been stupid because I was ashamed of having been taken in by a bad person and I didn't want my family to feel sorry that they hadn't been able to protect me or weren't able to read between the lines and see what was really going on. I am not a very strong person, I've thought about giving up in life more than once. To have the burden of having murdered a baby would have been too much for me to take. Other people's opinions about my morals are not important.
Maybe it's different because I've lost too many babies to miscarriage, I don't know - but those were all babies to me long before they could have been born alive. The parentage of the baby doesn't make him or her less of a human being.
I certaintly agree that it is not a good situation, and that there aren't good options. But I think it comes down to whether you believe abortion is murder, and if murder is worse (or not) than the inconvienence, stigma, extreme embarassment, lifelong resulting mental issues, etc.
I'm not unfeeling, and I understand the dilemma far more than you might think. Right now, any individual can make that choice.