That's because religious fanatics wouldn't like it. And we have more than our share of religious fanatics. Even though abortion isn't even in the bible. Not one word.
Another thing I noticed watching British ads was the existence of pregnancy test ads that don't present the women testing themselves as 100% wanting a baby and being thrilled that they're going to have one. There's ads with negative test results and couples going "woooooo!" (but in British).
I thought that was a well-done ad. Though, sure, people would take issue with it in the US, sadly. I still love the condom ad of the kid throwing a fit in the grocery store.
"I say, Jolly Good old chap!"