I totally agree on your ideas about romance lines and PSLs. If an organic romance line comes up in a game, I'd never knock it, but personally, I don't make a character and enter the community LOOKING for a romance line.
I guess most people work the opposite way though.
I think it also then comes down to mods and plot. When there's nothing else going on, characters tend to pair up and basically have a romantic PSL within the commmunity, and those who don't, wander off and hope for the best with the next game.