A few reasons: although rare, there are imperfections in condoms that can cause them to break. The morning after pill only has an effectiveness rate in the 80-something percentile range. If you're with the lucky woman who it's not working on, you're gonna have a nice fetus growing in your girl's womb.

Most women are not worse off because of birth control. It was originally developed to make periods more mild, and that is something it can do. It does have some side effects such as abnormal bleeding, weight gain, and possibly some other things which aren't so great. And if you go for methods such as the patch that use higher hormone dosages, there can be blood clots among other things.