Both genders are kept in the warrior castes to keep human reproduction intact. The clans are not trying to build a warrior caste that can only repopulate itself artificially. A lot of human psychology is control by hormones that effect human reproduction. Eliminating one effects the other.
I'll just quote Sarna which gets its info from the official source books:
"The use of
in vitro fertilization was also partially responsible for the casualness of love and relationships within Clan society, especially as the act of sex became divorced from reproduction. Whereas in the Inner Sphere such acts are considered a sign of intimacy in a relationship, among Clan warriors it is merely a normal part of friendship. The idea of sexual fidelity is completely lost on them as coupling with friends, usually members of the same
sibko, is completely natural. They also see the act of courtship as completely unnecessary and, if they bother to perform any type of seduction, are as likely to simply walk up to a complete stranger and ask if they are interested in coupling.
[24][25] As per the eugenics program, civilians are matched together based on their genetic compatibility, though the only purpose of these sanctioned matches is for the production of children; as a result promiscuity is also prevalent among the castes. A blind eye is turned to these "unofficial" couplings so long as birth control is used."
In short, the clans don't care about promiscuity and may even see it as a way to strengthen unity. Among the other castes, as long as childern are produced as assigned, no one cares about who else you sleep with or "love". Indecently, its still not unheard of for even Clan women of the warrior caste to have children. They can be reprimanded for doing so but the clans will let the child live and even allow them to become warriors. A cannon example of this would be Diana Pryde (who even managed to earn a bloodname because she was the child of two warrior castes members).
"The eugenics program proper began in
2819, though it wouldn't be until
2858 that the three distinctive phenotypes associated with modern-day trueborns first emerged.
[44] Surprisingly, scientists associated with the program take a hands-off approach to their work, preferring for the most part to let nature take its course. Genetic modification to alter physical or mental traits is used only sparingly beyond correcting adverse recessive traits or ensuring an equal balance of males and females to each Bloodhouse. This latter reason remains more for the sake of tradition than any true need, as it is relatively easy to take DNA from two individuals and splice them into sperm and ova gametes, creating a zygote irrespective of the donor's genes: theoretically a male warrior can be a "gene-mother" and vice versa, though again this is a rare occurrence. Another theoretical yet rarely occurring practice is the ability to create clones, known as a "retread." Simply replicating an individual however implies stagnation and goes against the Clans' belief in evolution and natural selection. Lastly Clan law discourages the combining of genes from related warriors, usually within three generations of each other; despite genetic screening incest remains a taboo."
In short, the clan eugenic program is governed by a lot of tradition and bioethical beliefs among the clans.
