I agree! But what games are you referring too? I think up to now the only rpg that successfully attempted to humanize and create believeable relationships between the characters is Dragon Age Origins.I like deep character interaction in RPGs. The main character acts, certain NPC react and a relationship forms. That can be friendship, hate, something in between, and it can be love. (If the sexual acts are shown explicitly or not isn't that important to me.)
Of course it is not a trivial thing to model something as complex as human realtionships in video games, but in my opinion it can be done well enough. Existing games have shown that.
But a role-playing-game that ignores things like this, just doesn't feel right to me. I don't want NPCs (especially companions) to be empty shells who just swing axes, throw fireballs or carry your stuff. I want to have an illusion of a real world with real characters.