Semen has controlling power over female genes and behaviour
Quite a long article into the positive effects of semen ingestion and absorption by women, but the most relevant point:
There have been claims that semen can do everything from making women sleepy after sex to strengthening the emotional bond with their partner. One 2002 study, based on a survey of 300 students, even found that women whose partners did not use condoms scored lower on a measure of depression.
If that effect is real, depression in some people might be treatable with artificial-semen suppositories.
For anal only couples, the suppository is unnecessary and the effects would be able to be replicated simply through ejaculation in the woman’s rectum, a process many are no doubt already doing anyway.