>>719228260
>bridges are a very important tool in crossing rivers
>okay smart guy, how do you build a bridge?
I don't have to answer a specific question in how to incorporate a mechanic after I already dislodged your idea that sex has somehow "no role in problem solving or conflict resolution".
I've provided adequate edivence to the contrary, how devs tackles this question is up to them personally and subjectively.

Look, I don't mean to be rude at all, but we're being pedantic here. Our current trends in western video games feature more violence as opposed to sex, but there's no real reason why that is given how important sex is in human history even when that's compared to violence.
Take something like the Sims, your goal is to make a family, obviously finding a mate and have sex is a pivotal point unless you consider adoption.
How would that become a mechanic? I don't know, a random event (Crusader Kings) that you want to get to continue your lineage in order to continue playing or maybe some QTE like in some japanese erotic games.
Maybe you could capture female enemy knights or commanders and get them pregnant so even if they escape they'll become useless for the next 9 months, which could win you a long campaign.