Due to the fact most New Texans are sterile thanks to their water being a contraceptive
Well technically, they're not sterile, the contraceptives have just lowered the impregnation rate drastically. Granted, the contraceptives would also play a pivotal role in the change of the role of condoms. Along with the breed happy aspect of the Treatment.
Though thanks to the magic of porn logic even that step isn't all that much hassle.
It's only as much of a problem as you make it, porn logic allows for writers to make characters as convenient and inconvenient as they wish!