Because they, men, did not want the responsibility of Ms. Jones and her baby in the morning.
Abortion was accepted as a means of birth control.
For some eggheads, that also means population control.
The biggest irony, second to our killing our own babies before God, is that the abortion "debate" has had the appearance of being about women choosing what they want to do.
When it was the men who made the laws up, in order to tidy up things at the office and elsewhere.
I have known single women who made a mistake and - on their own - decided to make the best of a bad sitution. (At least it seemed to be the best decision at the time.)
There is another big reason: women who want to have sex without responsibility for the consequences. It takes two.