At a guess because it results in a country that is closer to the one desired.

Never mind the fact that not a single abortion will be stopped on account of this. What will change is that there won't be any safe abortions, essentially this will cause the same number of fetuses to be aborted, it will also result in the death or in complications with a fairly large percentage of the mothers. It may (will?) even result in suicides.

This is in my opinion the real tragedy, the 'pro life' (I use their moniker but I disagree with it) groups are essentially 'anti mom'.