Ezekiel said:
What role does sex have in a story about defeating lots of people and accomplishing tasks?
That's a rather narrow, leading question. You might as well have asked 'what role does sex have in a game of Pacman'.
Violence is gamey. It can move a game along even when there is no story.
Gaming is an incredible diverse medium, and violence clearly is not the be all and end all. That it usually is reflects poorly on us and of writers and designers.
Witcher 2 is clearly a very violent game, but I always admired the choices it gives Geralt and the player in what was built as the final major showdown.
I've not played Watch Dogs 2 (yet), but I also admire the apparently robust options for a more pacifist playstyle. Action and gameplay systems can be enjoyed without casual, consequence-free murder being a primary gameplay loop (I feel it would've been more brave had Ubisoft ditched firearms entirely from the story - make a disdain for murder part of his character and the gameplay the player takes control of).
I see it (very rarely) used effectively in cutscenes, but I think cutscenes are far too overused and would prefer more minimalist stories that rely on environmental storytelling, the way only games can. Games don't need cutscenes and dialogue as much as the AAA publishers would have you believe.
That's fine for your own tastes, and I can certainly understand them; most major games are forever trapped within a thickheaded identity crisis, flip-flopping between passive and interactive - between simply sitting there watching filmic scenes and then actually 'playing' the thing. It's arguably a rather lazy form of design - relying on the ease and simplicity of passive sequences to flesh out what a dev's unable to do through mechanics, structure, other concepts, or environmental narrative, and so on.
But on t'other hand; gaming
is a unique mishmash of passive and interactive media. A film cannot ask for your input, neither can a book or sculpture. It's natural for gaming to take advantage of all that's available to it. That it's generally done lazily doesn't impact its essential merit (or potential).
Depending on the game, and what it's setting out to achieve, passive cutscenes are just fine.
For now, and this stage of the medium technologically? I think stuff like BioWare's 'sex' scenes get the job done; DA:I was a variously awful game [that I still ended up hugely enjoying when I sussed just how much of its vapid filler 'content' could be willfully ignored], but I felt the romance arcs were excellent (at least the one's I've seen so far). They represent progress in the right direction in terms of how relationships and sexuality's presented in a game's story (games very rarely even acknowledge that their cast members
have sexual orientations, preferences, opinions on sex, etc).
People pour scorn on some of BioWare's LI scenes, but frankly I'm more personally proud of the medium and its fans when people enthuse over empathetic emotional entanglements (which sex can be a part of) in a game as opposed to mindless violence and aggression, so, again, they are a step in a positive direction[footnote]...and no, to anyone who may get triggered by critique; empathetic emotional entanglements need not 'replace' mindless - typically masculinist - violence and aggression, but broader exploration of the spectrum is important for the medium's health.[/footnote].