I remember an old telenovela where the catch phrase was:
"Las chicas buenas se van al cielo, las malas a donde les da la gana" or something like that.
Meaning that good girls go to heaven but the bad ones wherever they want to. It was such a good change of pace.
I think it's mostly because in romance love is seen in a pure way, like in a non smut yuri. All is more innocent, so they don't talk so much about their sexualities, but it is not so close to real life.
I think it is also because in more conservative societies people are taught that they should be like that, especially women, just with one partner forever and ever, so sometimes they don't even question theirselves. Until something happens, and I think that's called midlife crisis lol