Depends on the group/players really.
In my world setting fo Orea, satyrs are a playable PC race. So oftentimes, the player that wants tto be a satyr is...well...a "playuh"...horny lil' goats. But then there've been PCs who are particuarly randy beings of any race.
Homosexuality is a kinda regular occurrance, viewed as normal in some societies less so in others. Elves, in general, are pretty "free love" kinda folks.
There's a lot of flirting, "hitting on", double entendre, perhaps the occasional rendezvous. But like many here, it sounds like, that's the "fade to black" or "[jump to] so the following morning..." Nothing particularly sexual is ever "seen" at the table.
There have been times when two PCs have started something...that seems a bit more common in my games than a PC and NPC becoming involved. Even a marriage or two...but generally, it levels out at the "serious committed relationships" stage and doesn't often get to the full on "wedding/religious union". All kinds of gender (and race) mixes.
I don't mind it (long as the players keep it mature) and it usually lends a bit more drama and tension if, for example, someone ends up wounded badly or dead...or gets captured/separated...or does very well with something (Having reasons to celebrate is just as important as reasons to cry or worry.
But, in the grand scheme of simple numbers of characters (PC and NPC) and interactions that there have been over the years, the number of actual relationship/romance type situations (vs. "one-night-stand" or womanizing) that come up and been a part of play is fairly minor (versus just two players saying "and our PCs are a couple"...but then they never show/RP that and its effectively the same as the vast majority NOT being a couple).