Scenes like these happen but the reason they aren't more common is that only a very small percentage of the playerbase can even get them. Of course, when the super specific scene is right up your alley it's awesome. But all the writing time spent on that super specific scene that appeals to 5% of the player base is time not spent on scenes that appeal to the majority, or even 40%, or 20%, etc. There is an opportunity cost to everything.
More often there are fleshed-out variants for scenes instead. Off the top of my head there is a Brienne scene where if you're very tall and/or very high strength you can pick her up. If you're not, she rides you (I think?).