Point is there is already a form of male birth control. So if a man doesn’t want to be a father he can take precautions for himself (if he doesn’t want to keep it zipped) and not have to rely on the woman’s word that she is on the pill or otherwise infertile at the time.
A woman can hold her knees together also. So if a woman doesn’t want to be a mother she can take precautions for herself. If she doesn’t want to keep her knees together, the state will the father paid for by taxes paid by men.