I think there just isn't enough time dedicated to relationship building. Even if a game is over 10 hours long, a good chunk of that will be spent running around killing things. Not exactly romantic.

A lot of games also happen within a short space of time, or have no sense of time at all. Love needs that pacing to feel realistic.

Because films are light years ahead of video games when it comes to writing, characterization, dialogue, acting, etc. As much as some gamers would hope for, that will probably always be the case.

Even most movies have trouble depicting love, to be perfectly honest, because 90% of the time it is only depicted as the stage 1 "sexual attraction" portion of relationships.

Not that there's anything wrong with that, but if the question is "why can games not depict love?" then the answer is because most writers are incapable of producing a love narrative that is anymore deep or meaningful than what can be found in the first fifteen minutes of cheap softcore porn.

I have a feeling that most people are really only considering the hypocrisy of being able to depict violence so openly and not nudity / sexuality, so I suppose it's all kinda moot.

It ain’t great.