How can pregnancy be a surprise?

Steph
In 32 years old and fairly intelligent - I don't understand how pregnancy can be a surprise! Maybe I'm naive but I just don't see how, aside from medical conditions, women can be shocked they are pregnant! Please share your stories!!! I have been using my trusty pull out method for years, and surprise - no baby!!! Does bc actually fail? I love the surprise stories, they make me happy, I just don't see how it could be a total out of the blue shock