Sure, romance has been in a good few FF games. Perhaps I haven't been specific enough, FF games never have the player in charge of developing or influencing the characters. The player's job is to just make sure that the characters stay alive against the baddies, and listens to what they have to say during lapses in the baddie killing. You can't add much flexibility with character interactions in this style of RPG..
When it comes to the concept of the player interacting with characters and developing a "romance" from these interactions, games haven't really gone very far. BGII is probably the best example of interactive romance in RPGs, and I think this did a good job adding depth to the characters and the game. Sure, you didn't even have to get involved with anyone, but the fact that these extra interactions with certain characters existed, gave good reason to play through the game again. That's a big sign of a good RPG I believe; there being enough depth to motivate you enough to play the game several times over. Lastly, these choices made BGII feel less like "just another computer game", and more like an epic story with believable people.
Even BGII didn't cover nearly every romance-RPG concept though. As I recall, after falling in love with an NPC, you HAD to break it off for whatever reason, regardless of who the NPC was. In future games, it would be interesting for instance, to have two characters fall in love mid-way through, and then seeing if the relationship actually holds strong right up to the end of the game through further interaction and events.
You're correct about the depth/choice problem, though. I imagine the only real way to work around this is to just spend tons of time creating tons of different possible interactions and relationships to cater to everyone. Still, there's no need to go backwards and have no romances at all.
I think that's my point. Maybe not, who cares!