I had typed out something about this yesterday but it got et.
I have thought about why I was super uncomfortable with NPC sexual/romantic play with PCs in my earlier-to-mid MUSHing years but it really doesn't bother me at all now.
I think it is because back in my "growing up" years on games, because sexual RP was so (prevelent but) looked down upon and shamed, and because at least on my formative games at that time (oWoD and Shadowrun) you really didn't have people who weren't staff running plot or scenes, it was extremely hard for people to say no safely to staff. And especially once the risky play of sexual themes entered it was even harder to say no/let's do something else or do anything that would lead to exposure for engaging in that play. Particularly if you were female.
It took me many years even after I started playing on games where sexual RP was /not/ particularly shamed to not have that discomfort. Possibly because even today in the community, you do have the slut-shaming/OMG this worthless person who only TSes, ect stuff that goes on, though fortunately not to the same extent.
But now I simply don't play on games if I don't feel the staff is safe. This is a relatively new development in my MUSHing life. While by no means have I agreed with every staff decision on the main game I play on, and yes I have not infrequently been annoyed at times with the time/energy lavished on people who just seem to return that with rudeness and entitlement and just...obnoxiousness--the truth is that I feel very safe on that game from a The Staff I Interact With Have a Strong Baseline of Trust I'm Willing to Give Them standpoint. While having any NPC played more like a PC is not a decision I personally would have made, it doesn't bother me because of my high degree of trust. It is probable on another game it would, though I am not sure it would mean I'd walk out.
So I don't really care if they're having orgies with other people, because I see sexual and/or romantic RP as legitimate stories. To be honest, I would have more fun engaging in horribad unintentionally hilarious TS than I do in many meeting/large social scenes. Pillow talk is just as likely a funnel for gossip as is blabbing about stuff at a cafe or in sparring banter. There's room for all of it, IMO.