Because when it comes to bearing children, women can make any choice they want but men cannot.
Women have, just off of the top of my head: birth control, IUDs, depo shots, hysterectomies, Plan B, abortion (though that one is contentious), safe haven laws, adoption, etc. Women don’t have to be a mother if they don’t want to, regardless of what the man wants. But the reverse is anything but true.
And that would be fine. Except we make men pay for women’s choices here. Historically we have tied the commitment of marriage as consent to support a family. But now that we don’t, it perfectly legal for a woman to turkey-baste semen from oral sex into her vagina, become pregnant, and then obtain child support from the man — its happened at least once.
I don’t see that as very fair or respectful of bodily autonomy. Do you?