Sexuality has been a fairly dead issue in RPGs for some time. We do see the occasional game like Ironwood that makes sex an issue, but no games with anything as crass as rules to govern these interactions. Why not? If we agree that sexuality is a huge force in human history and experience, then why has it never been dealt with openly, rationally, or at least maturely?
Contrast with this:
No one could ever accuse RPG characters of having boring lives.