Abstinence is the only method of birth control with a 100% effectiveness rate. It literally works every time it’s tried!
Aye, there’s the rub. How often is it tried?
I come at this as a man who knows that, as far as the law is concerned, I need to be prepared to support the child that could result from ANY sexual encounter I have. No ifs, ands, or buts. It’s a great incentive to use the 100% effective method if I have any doubts about my desire to create a child.
(Several possible puns in that message - none were intended.)
If you don't count that one time about 2,008 years ago...