I've run a number of successful campaigns in which romance figured quite prominently... between PCs and PC/NPCs alike. It is, in my experience, an undeniably potent element of high fantasy, and most of my players tend to be purists... for whom a playing experience that has no option to explore such things would seem shallow and incomplete. Not to say that every player jumps on any opportunity to explore such relationships, but even though we've never actually discussed the place (or lack thereof) of such elements in gameplay, I think that my players would, by and large, be enormously surprised to discover that such concepts are strictly off-limits for some gaming groups. It's kind of like meta-gaming away some defining aspect of characterization, leaving the player unable to organically pursue the growth of his/her character.
Perhaps it helps that I've rather persistently enjoyed player groups of a mixed gender... but I think it's just the breed of player that's developed during my years of gaming. A player who wants to explore every important experience of a character's life to some degree or another.
I think my crowning achievement, for example, was a roleplaying situation during which, over the course of about a dozen sessions, I inspired a PC who had been tragically blinded in an earlier encounter to fall desperately in love with the woman who elected to tend to him and keep him company, despite the fact that he could not see her.... That player, who never once seemed uncomfortable during the roleplay encounters involved because he was so into the character, was certainly not the type who would seem responsive to such developments in-game... and to this day, he wonders how it happened.